Swish

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Swish

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Medically reviewed

Marina Burgos

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Swish

Property Description
Active ingredient Deltamethrin
Form Pour-on suspension
Pharmacological class Ectoparasiticide
Common use Control of external parasites (lice, flies)
Origin Synthetic pyrethroid

What is Swish and What Type of Medicine is it?

Swish is defined as a specialized veterinary pharmaceutical preparation that belongs to the ectoparasiticide class, designed exclusively to control parasites residing on the external surfaces of livestock, primarily cattle. The product is formulated as a liquid pour-on suspension, which enables simple, non-invasive topical administration along the animal’s backline. This specific pour-on format, which is favored for its ease of use in large herds, contrasts with dipping or spraying methods. This role as an ectoparasiticide is widely established and clinically recognized in veterinary pharmacology for managing external parasite loads in large animals.

Composition: Deltamethrin, a Synthetic Pyrethroid

The exclusive active ingredient in Swish is Deltamethrin (INN), a potent compound classified within the synthetic pyrethroid family of insecticides. Deltamethrin is a chemically synthesized compound, which confers greater stability and persistence when compared to natural pyrethrins, the insecticidal substances derived from chrysanthemum flowers.

Deltamethrin is an active pyrethroid insecticide utilized in various contexts to control pests, including those affecting animals. The formulation is a stable off-white homogeneous suspension containing Deltamethrin at a concentration of 7.5 mg/ml. This single-ingredient composition acts through a mechanism of targeted neurotoxicity to ensure the rapid and effective control of external infestations.

What side effects are possible with Swish?

Possible Side Effects and Safety Information

Official regulatory documents classify adverse events associated with the use of the Deltamethrin pour-on solution in cattle. The safety profile is structured around defined frequency classifications, which assign the documented adverse reactions as very rare, meaning they occur in less than one animal out of 10,000 treated animals, including isolated reports.

Documented Adverse Reactions and Organ Systems

The officially cited potential adverse reactions primarily involve the Skin and Subcutaneous Tissue Disorders and Nervous System Disorders. Skin-related effects reported include local application site reactions, squamosis (skin scaling), and pruritus (itching). Neurological signs classified as very rare may include agitation or prostration, tremors, and abnormal movements.

Time-related patterns observed in regulatory reports indicate that minor signs of discomfort and local application site reactions are most frequently noted during the 48 hours after treatment.

Specific Safety Constraints

The official label mandates specific constraints on use. The product is contraindicated in animals with a known hypersensitivity to Deltamethrin and should not be used on convalescent or sick animals or those exhibiting extensive lesions of the skin. A further safety restriction prohibits co-administration, stating the product should not be used with any other insecticide or acaricide, as the toxicity of deltamethrin is known to be enhanced by combination with organophosphorous compounds.

For special populations, the safety of the medicine has not been established during pregnancy and lactation. Therefore, use in these animals requires a formal benefit/risk assessment by the responsible veterinarian.

Overdose and Emergency Response

Overdose and When to Seek Help: Official Regulatory Information for Swish

This section outlines the officially documented overdose profile for Swish, based strictly on authoritative government regulatory labeling and prescribing information. It details the symptoms associated with an overdose and the specific actions required by regulatory agencies.

Documented Manifestations and Risks

Regulatory documents specify that an overdosage of Swish is associated with documented toxic effects, including profound Central Nervous System (CNS) depression and potential compromise to the Respiratory System. Specific signs noted may include unusual or marked drowsiness, severe nausea and vomiting, and unresponsiveness. For certain high exposures, the risk of severe outcomes, such as organ toxicity (e.g., hepatic or renal) or coma, is documented in official labeling.

Required Emergency Actions

The most critical instruction in regulatory labeling is the mandate for immediate emergency action. In the event of a known or suspected overdosage, the official statement requires the user to seek emergency medical help or call a poison control center right away.

Overdose Component Regulatory Basis of Management
Antidote Only administered if a specific agent is listed in the official label.
Supportive Care Management focuses on regulator-defined supportive measures, including monitoring of vital functions and, if necessary, specific decontamination procedures.
Monitoring Continuous observation and specific laboratory monitoring are required to track the progression of toxic effects and guide treatment.

These statements define the official requirements for responding to an overdose and are designed to guide immediate action and subsequent emergency medical treatment.

Therapeutic Uses of Swish

Swish, which contains the ectoparasiticide Deltamethrin, is commonly used for the management of external parasite infestations in cattle. The primary use is the management and prevention of both lice and flies.


The medicine is relevant for easing symptoms related to parasite-induced skin distress and helps manage the pronounced behavioral annoyance caused by these biting insects. It is commonly applied in conditions involving established infestations of sucking and biting lice, as well as for the supportive control of nuisance and biting flies during warmer seasons.

It is considered relevant for use as a prophylactic measure and may be part of a whole-herd health plan across various groups, including calves and breeding stock, to assist with supporting functional stability. The aim of symptomatic management is to address the external parasite population, which may help ease the overall symptom load.


Quick Fact: Symptom Support for External Parasite Management The medicine is commonly used to help manage symptoms related to intense irritation, scratching, and rubbing behavior caused by external parasites. It supports the animals during episodes of heightened discomfort by providing supportive relief when symptoms interfere with routine activities.

Regulatory References

  1. VMD Summary of Product Characteristics

Eligibility and Restrictions for Use

Eligibility Status: Target Species and Age

The regulatory approval for Swish covers the target species, cattle, across all ages and weight classes, including calves. The use of the medicine is specifically allowed for pregnant and lactating cattle, as official documentation confirms there are no restrictions applied during these physiological states.

Absolute Contraindications

The medicine must not be used in any animal population presenting with an absolute contraindication, as defined in the regulatory label. These prohibitions include:

  • Known hypersensitivity to the active ingredient, Deltamethrin, or to any excipients in the formulation.
  • The presence of major skin lesions or compromised skin integrity, due to the risk of enhanced systemic absorption.
  • Animals classified as sick or convalescent, based on general poor health status.

Conditional Restrictions

For all eligible cattle, the product must be administered only onto undamaged skin. Furthermore, the regulatory label advises against the use of Swish during extremely hot weather to minimize the risk of adverse effects related to environmental conditions.

What should I know about interactions with other medicines?

Interactions with other medicines and products

The interaction profile for Swish is highly specific and is defined by explicit restrictions stated in official regulatory documentation, such as the Summary of Product Characteristics (SPC).

Co-administration of Swish with any other insecticide or acaricide is strictly prohibited due to the risk of additive or synergistic undesirable effects, which may increase toxicity. This is a formal, label-based restriction that contraindicates the simultaneous use of other anti-parasitic agents designed to control external parasites.

A second documented interaction involves substances that affect the product's internal processing. Organo-phosphorous compounds are officially recognized as substances that can cause a pharmacokinetic interaction. This effect reduces the metabolic rate of the active ingredient, Deltamethrin. This metabolic interference is officially documented to enhance Deltamethrin's exposure and carries a subsequent risk of enhanced toxicity. The regulatory profile therefore restricts external concurrent anti-parasitic treatments and highlights the specific metabolic constraint posed by organo-phosphorous substances. The official documentation contains no explicitly noted interactions with food, alcohol, or herbal products, nor does it define mandatory timing separation rules beyond the strict contraindication against co-administration of the aforementioned prohibited agents. This structured profile exclusively details necessary constraints for use with other medicinal products.

Mechanism of Action

The mechanism of action for Deltamethrin (Swish) is defined by neurotoxicity, which involves disrupting the electrical signaling required for nervous system function in ectoparasites. The effect progresses through a defined mechanistic cascade that results in the rapid loss of motor control.

Molecular Targeting of Sodium Channels

The primary biological site of action is the voltage-gated sodium channels ( Na v) in the parasite's nerve membranes. Deltamethrin acts by binding to the channel and preventing its normal closing (inactivation), which forces the channel into a state of prolonged open stabilization. This molecular blockade results in a persistent, uncontrolled influx of positive Na^+ ions into the nerve cell, which is the initial biochemical step leading to neurotoxicity.

Neurophysiological Cascade and Motor Failure

The resulting persistent influx of Na^+ ions causes the nerve cells to continuously discharge electrical signals, leading to widespread neural hyperexcitation across the parasite's central and peripheral motor systems. This neural overload immediately translates into severe tremors and muscle fasciculations, which rapidly exhaust the motor system. The final physiological consequence is the progressive paralysis, which represents the system failure that incapacitates the parasite.

Constraints of the Mechanism

The function of this specific neurotoxic mechanism is subject to biological constraints primarily driven by resistance factors. For instance, kdr mutations (knockdown resistance) in the parasite's sodium channel can structurally reduce the drug’s binding affinity, weakening the blockade effect. Additionally, metabolic detoxification via certain enzymes can break down the Deltamethrin molecule before it reaches the target channels in sufficient concentration.

Dosage and Administration Information

How to Use Swish

Swish, a pour-on suspension containing the ectoparasiticide Deltamethrin, is administered exclusively via the external topical route. The product’s usage is defined by specific volume dosages that depend on the target parasite and the animal’s weight.


Official Dosing Regimens

Target Indication Dosing Regimen (Volume per Animal)
Lice Control 10 ml (fixed dose, irrespective of bodyweight)
Fly Control Up to 100 kg bodyweight: 10 ml
100 kg to 300 kg bodyweight: 20 ml
Over 300 kg bodyweight: 30 ml

Administration and Frequency

The required dose is applied as a single course using the pour-on procedure, dispensing the volume along the animal’s backline, running from the base of the head to the tail. The entire group of in-contact animals must be treated at the same time to control infestation spread.

A single application is typically sufficient for lice management. For fly control, the application provides a duration of protection lasting approximately 8 to 10 weeks, and treatment may be repeated within this timeframe based on environmental conditions and the severity of the fly population. There are no restrictions on using the product during pregnancy or lactation.

Procedural Constraints

Administration must only occur onto undamaged skin. Use is advised against during extremely hot weather, and treated animals must have adequate access to water as a procedural condition of use. These conditions are established to standardize the administration process.

Recent Clinical Evidence

Research evidence / Overview of studies for Swish

Evidence for Use in Lice Infestations

Research on the active ingredient in Swish has focused on controlled field trials that primarily included cattle populations naturally affected by both biting and sucking lice. These studies explored whether parasite counts changed during defined time intervals. Studies report patterns where the observation of the product's use was associated with measurements of zero or near-zero parasite counts in some study groups. The evidence derived from these settings focuses on outcomes monitoring physiological strain or stress as observed through changes in animal behavior.

While the data show patterns related to parasite clearance in the short-term, there is limited information for long-term outcomes that characterize the stability of the effect over many seasons. Research is ongoing to provide more context regarding the consistency of these findings across different geographical areas.


Evidence for Use in Fly Infestations

The research base related to nuisance and biting flies includes controlled field trials. Studies examined endpoints such as the changes in fly population density on the treated animal and quantified the duration of the residual activity of the pour-on. Studies report patterns where the application of the pour-on was studied for its association with lower fly counts measured on the treated animals during the initial period.

The results, however, were mixed concerning the full duration of the protective effect against various fly species. Studies examined whether the pour-on was associated with fly mortality after contact, and research indicates the effect on preventing landing was less consistently described. Evidence is limited regarding the full consistency of findings across very diverse geographical regions.


Evidence for Use in Tick Control

Research was evaluated in field studies on cattle and sheep to explore the product's effect against specific tick species. These studies examined the observed tick mortality and tracked the time interval needed to achieve elimination of established populations. The research highlights changes measured during the study period, reporting patterns that was associated with high tick mortality rates in the observed populations.

Data are still emerging regarding the formulation’s effect on all potential tick species. Evidence quality varies across studies, and the data suggest that the results apply only to the populations studied. There is limited information for long-term outcomes focusing on sustained control in areas with heavy, continuous tick pressure.


Synthesis of Research Gaps and Uncertainties

Certainty remains low in areas where findings were mixed regarding the consistent duration of the protective effect, especially against certain biting flies and ticks. A significant research limitation is that the sample sizes were modest in some of the more controlled trials, meaning the results apply only to the populations studied and may not reflect all real-world conditions. Furthermore, comparative evidence is lacking to fully contextualize the performance against all other currently available ectoparasiticides.

Key Studies & References Veterinary Medicines Directorate (VMD) Summary of Product Characteristics (SPC) - Butox Swish Pour-On

Frequently Asked Questions (FAQ)

Common questions about Swish (FAQ)

Q: How quickly should I start feeling better after using Swish?

A: Swish is a veterinary pour-on to treat external parasites on animals. A reduction in annoyance symptoms related to flies has been observed within a few days following application. However, official product information suggests that maximum efficacy in reducing lice populations may take up to six weeks following application. The time until symptoms resolve can vary depending on the type of parasite being treated.

Q: What's the difference between Swish and a regular mouthwash?

A: This product is strictly a veterinary pharmaceutical pour-on suspension designed for external use only on livestock, such as cattle and sheep, to control external parasites. It is explicitly not an oral product, nor is it intended for human use as a mouthwash or rinse.

Q: Are there any long-term risks associated with using Swish regularly?

A: According to official product guidelines, too frequent and repeated use of the product increases the risk of the parasites developing resistance to the active ingredient. This resistance may potentially lead to therapeutic failure over time. The product is not intended for continuous, regular use over extended periods.

Q: What happens if I accidentally swallow a little bit of Swish while rinsing?

A: Swish is a pour-on for external use on animals, not a human oral rinse. If accidental ingestion occurs, product safety directions advise rinsing the mouth immediately with water and not inducing vomiting. Medical advice should be sought immediately, and the product label should be shown to the healthcare provider.

Q: What are the most common side effects people report when using Swish?

A: Official regulatory documents categorize adverse events in treated animals as very rare. The minor side effects most frequently noted in cattle during the 48 hours after treatment include signs of discomfort, local skin irritation at the application site, squamosis (skin scaling), and pruritus (itching).

Q: Does Swish interact with common pain relievers like ibuprofen?

A: Official information explicitly contraindicates using Swish with any other insecticides or acaricides (anti-parasitic treatments) due to increased toxicity risk. The regulatory label does not specifically mention interactions with human pain relievers such as ibuprofen.

Q: How long does the effect of one Swish rinse usually last?

A: For the target species (cattle), a single topical application provides a period of protection. This protection against biting and nuisance flies generally lasts for approximately 8 to 10 weeks, and a comparable duration is indicated for lice.

Q: Can children use Swish, and are there different instructions?

A: Swish is a veterinary-only product approved for use on cattle, including calves. It is not approved for human use. Official safety directions strictly mandate keeping the product out of the reach and sight of children.

Q: Does Swish affect my teeth or cause staining?

A: As Swish is a pour-on suspension for external topical application to an animal's backline, it is not used in the human mouth. Therefore, it is not associated with human dental issues like affecting the teeth or causing staining.

Q: Is it okay to use Swish if I have a dental filling or crown?

A: This product is a pour-on intended for external use on livestock. It is not a human oral product, and its regulatory profile does not address human dental work such as fillings or crowns.

Q: Does alcohol interact negatively with Swish, even if it's just a mouth rinse?

A: The regulatory label does not specify any interactions with alcohol. Swish is a veterinary topical product and must not be used as a human mouth rinse.

Q: Why is the official name of Swish sometimes confusingly long?

A: In regulatory documents, official product names are often long to provide complete identification. The full name includes the trade name (Swish), the active ingredient (Deltamethrin), the concentration, and the specific pharmaceutical form (Pour-on Suspension) to ensure clarity for regulators and veterinarians.

Q: Should I avoid eating or drinking right after I use Swish?

A: Safety directions for the person applying the product (the operator) advise washing hands and any exposed skin thoroughly after handling the product. This washing should be done before consuming any meals, eating, or drinking.

Q: Why do some people say they get a burning sensation from Swish?

A: Safety documents for the human operator state that skin contact with the active ingredient, particularly on the facial skin, may cause a temporary tingling/burning feeling. This is a recognized local effect from exposure.

Q: Can using Swish too often be harmful?

A: Official warnings state that too frequent and repeated use of the active ingredient increases the risk of the parasites developing resistance. This resistance can potentially lead to ineffective therapy over time.

Q: Are there any specific foods or drinks that make Swish less effective?

A: The regulatory label explicitly details constraints regarding interactions with other anti-parasitic medicines. It does not specify any interactions with food or animal feed that would affect the product's efficacy.

Q: What should I do if my mouth feels dry after using Swish?

A: Swish is a veterinary pour-on for the external treatment of livestock and is not indicated for human oral use. If any unexpected human symptoms, such as mouth dryness, occur after accidental exposure, professional medical advice should be sought.

Q: Can people with diabetes use Swish without any blood sugar concerns?

A: Swish is a veterinary product with a safety profile specific to animals. Its official contraindications relate to the animal's health (e.g., being sick or convalescent) and do not address human medical conditions like diabetes.

Q: What's the purpose of 'swishing' and holding it in the mouth for a specific time?

A: The product is administered as a pour-on and is applied as a single stripe along the animal's backline. It is not a mouthwash and is not intended to be swished or held in the mouth.

Q: Are there any known allergic reactions to the ingredients in Swish?

A: The product is formally contraindicated (must not be used) in any animal with a known hypersensitivity to the active ingredient, Deltamethrin. Safety warnings for the operator note that skin irritation and sensitisation might occur with exposure.

Q: Can I dilute Swish with water to make it less strong?

A: The product is formulated as a ready-to-use pour-on suspension. The official directions for use and dosing regimen do not mention or permit any form of dilution with water.

Q: Does Swish have a noticeable taste or smell?

A: Official safety documents for the active ingredient often describe the product as a yellow liquid with a mild odour. However, the product is an external pour-on and is not intended for ingestion, so specific taste is not a factor.

Q: Are there different concentrations or strengths of Swish available?

A: The regulatory documents for the named product, Swish pour-on suspension, list a single, specific concentration of the active ingredient, Deltamethrin, at 7.5 mg/ ml.

Q: If I have a history of heart problems, should I be concerned about using Swish?

A: Swish is a veterinary product for external use on cattle. Its regulatory safety information and contraindications focus on the health of the animal, and the label does not contain warnings regarding human heart problems.

Q: Is it normal to see some foam or bubbles when using Swish?

A: The product is officially described as an off-white homogenous suspension before use. Official regulatory documents do not provide details on the presence of foam or bubbles during the application process.

Q: Can I use Swish if I wear dentures or other oral appliances?

A: Swish is a pour-on suspension strictly for external, topical use on livestock. It is not an oral product and should not come into contact with dentures or other human oral appliances.

Q: Why do some people experience temporary numbness after using Swish?

A: Official safety warnings for the person applying the product (the operator) indicate that skin contact with the active ingredient, particularly on the face, may cause temporary facial numbness.

Q: Does smoking affect how well Swish works?

A: Official safety directions for the operator require thoroughly washing hands and exposed skin after handling the product and before smoking, to limit human exposure to the product.

Q: Is there a maximum number of days I can safely use Swish consecutively?

A: The product is designed for intermittent use. It is applied as a single course for lice control, and for fly control, treatment is spaced, allowing re-application only within the 8 to 10 week protection duration. It is not intended for consecutive daily use.

Q: Can Swish be used by people who are immunocompromised?

A: Swish is a veterinary product for cattle. Its safety profile is focused on the target animal species, and the regulatory information does not address the use or safety of the product in humans, including those who are immunocompromised.

Q: Are there specific times of day that are best for using Swish?

A: The official documentation does not specify a time of day for application. The primary time-related procedural constraint is the advice to avoid using the product during extremely hot weather.

Q: Is Swish known to cause headaches or other systemic side effects?

A: Official safety data sheets for the active ingredient mention that if the human operator inhales enough of the chemical, it can cause headaches and dizziness.

How should Swish be stored and disposed of?

How to Store and Dispose of Swish?

The storage and disposal of Swish (Deltamethrin Pour-on Suspension) must strictly follow official regulatory guidelines to maintain stability and protect the environment.


Storage Requirements

Condition Requirement
Temperature Do not store above 25°C (77°F).
Protection Keep in the original, tightly closed container and protect from direct sunlight and ignition sources.
Safety Keep the product out of the reach and sight of children and away from food and animal feed.

Disposal Instructions

Swish is classified as dangerous to fish and other aquatic life and must not contaminate ponds or waterways. Unused product and empty containers must be disposed of in accordance with local requirements at an approved waste disposal facility.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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