Ingredient review
Pyrethrins
INCI: Pyrethrins
Pyrethrins are effective insecticides but are not recommended for routine skincare due to high irritation potential and lack of skin benefits.
In plain English
Pyrethrins are natural chemicals from a type of chrysanthemum flower that kill insects. They are sometimes used in lice shampoos or pet flea treatments, but they are not a typical skincare ingredient. In fact, they can cause stinging, redness, or allergic reactions on skin, so they are best avoided in everyday face or body products.
Review score
Safety, usefulness, and evidence
Higher-caution ingredient
The evidence base is useful, but some claims depend heavily on the formula.
Main practical flags: irritation is high; clogging risk is low.
- Source
- natural
- Evidence
- moderate
- Irritation
- high
- Clogging risk
- low
Quick decision guide
Read the cautions before using
Pyrethrins can be useful, but watch for high irritation potential.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Pyrethrins.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
highMore likely to cause dryness, stinging, peeling, or reactivity if used too aggressively.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
Pyrethrins are a group of six naturally occurring compounds extracted from the dried flowers of Chrysanthemum cinerariifolium. They act as neurotoxins to insects, disrupting their nervous system.
How it works
In a cosmetic product, pyrethrins target the nervous system of insects like lice or mites, causing paralysis and death. On human skin, they have no beneficial cosmetic function and can instead trigger irritation or allergic contact dermatitis.
Pros
Proven insecticide
Pyrethrins are well-studied and effective at killing lice, mites, and other insects quickly, making them useful in medicated shampoos.
Naturally derived
Extracted from chrysanthemum flowers, pyrethrins are a plant-based alternative to synthetic insecticides like permethrin.
Cons and cautions
High irritation risk
Pyrethrins can cause stinging, redness, and allergic contact dermatitis, especially on sensitive or broken skin. They are not suitable for daily skincare.
No skincare benefit
Unlike moisturizers or antioxidants, pyrethrins offer no hydrating, anti-aging, or soothing properties. They serve only as an insecticide.
Best for
- Anyone treating a confirmed head lice or scabies infestation under medical guidance
- People using a rinse-off product specifically formulated for insect control
Use caution if
- Anyone with sensitive, eczema-prone, or damaged skin
- Pregnant or breastfeeding individuals (unless directed by a doctor)
- People using leave-on facial or body skincare products
Usage tips
Safety summary
Pyrethrins are safe for occasional, short-term use as an insecticide in rinse-off products when used as directed. However, they pose a high risk of skin irritation and allergic reactions, especially for individuals with sensitive skin or eczema. They are not recommended for leave-on skincare or daily use.
Research notes
Multiple studies confirm pyrethrins' efficacy against head lice and scabies. However, research also documents cases of allergic contact dermatitis and respiratory irritation. The evidence supports their use only as a targeted insecticide, not as a general cosmetic ingredient.
Common label clues
- Typical concentration
- 0.1% to 0.5% in rinse-off products; rarely in leave-on skincare
- Regulatory status
- Approved by the U.S. EPA as an insecticide for topical use on humans. The FDA regulates pyrethrin-containing products as over-the-counter drugs for lice treatment. Not approved as a general cosmetic ingredient.
- Common uses
- Anti-lice treatments, Pet shampoos, Insect repellent products
- Environmental note
- Pyrethrins are biodegradable and break down quickly in sunlight, but they are highly toxic to aquatic life and bees. Disposal should follow local guidelines.
Good to know
- Pyrethrins are often combined with piperonyl butoxide (PBO) to enhance insecticidal activity.
- Synthetic versions called pyrethroids (e.g., permethrin) are more stable and commonly used in topical treatments.
Common questions
What is Pyrethrins in beauty products?
Pyrethrins are natural chemicals from a type of chrysanthemum flower that kill insects. They are sometimes used in lice shampoos or pet flea treatments, but they are not a typical skincare ingredient. In fact, they can cause stinging, redness, or allergic reactions on skin, so they are best avoided in everyday face or body products.
What does Pyrethrins do in a beauty product?
In a cosmetic product, pyrethrins target the nervous system of insects like lice or mites, causing paralysis and death. On human skin, they have no beneficial cosmetic function and can instead trigger irritation or allergic contact dermatitis.
Is Pyrethrins safe for most people?
Pyrethrins are safe for occasional, short-term use as an insecticide in rinse-off products when used as directed. However, they pose a high risk of skin irritation and allergic reactions, especially for individuals with sensitive skin or eczema. They are not recommended for leave-on skincare or daily use.
Who should be careful with Pyrethrins?
Anyone with sensitive, eczema-prone, or damaged skin Pregnant or breastfeeding individuals (unless directed by a doctor) People using leave-on facial or body skincare products
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.