How Effective is IR3535, and Why We Chose It for Our Baby Cream

When you become a parent, one question tends to arrive with your first evening walk with the pram: what do you put on a baby’s skin to keep the mosquitoes away? A baby’s skin is doing very different work from yours, and the answer matters.

At The Naturally Kind Co. we spent a long time on this exact question before we settled on our Skin Shield Baby Cream. Our answer is an organic base paired with a small addition of IR3535, labelled on our box as Butylacetylaminopropionate.

What is IR3535?

IR3535 (ethyl butylacetylaminopropionate) is a repellent active ingredient developed by Merck and used across Europe and the US for decades. Chemically it is modelled on an amino acid that occurs naturally in the body, which is why it is so well tolerated across ages.

It is not DEET. It is not picaridin. It sits in its own small family of repellents, considered mild but genuinely effective against mosquitoes, biting flies and ticks. That combination of a gentle skin story and real biting-insect performance is exactly what a baby-focused formula needs.

Why we added it to Skin Shield Baby Cream

For babies under one year old, essential-oil-only formulas at effective concentrations are not appropriate for young skin. So we had two options: a formula needing reapplication every 30 to 45 minutes, or a small addition of a well-studied active that carries the protection further. We chose the second because a baby-focused product should protect a baby for a meaningful window of time.

What the health authorities say

The US EPA classifies IR3535 as low toxicity and permits its use in products for children. The World Health Organisation includes it among the actives it considers appropriate for protection against biting insects. Public health bodies across the EU authorise it for family repellent products from 2 months and above.

That 2-month age point is where our Skin Shield Baby Cream begins. Under 2 months, use physical protection: light cotton clothing, a fine pram net, and avoid the busiest biting hours.

How to use it

Squeeze a small amount onto your fingertips and smooth gently over your baby’s exposed skin. Focus on arms, legs, ankles and the back of the neck. Avoid the eye area, lips and any broken skin. Patch-test on the inner arm and wait 24 hours before broader use. Wash off at the end of the day with baby’s usual soap and warm water.

What’s next

IR3535 currently sits only in our Baby Cream. Our Skin Shield sprays, FlyFree, FlyDefence, TickFree and Haven Oil rely entirely on essential-oil actives. That said, our R&D team is now working with a view to adding IR3535 across more of our skin and coat repellent products.

Ready to try our Baby Cream? Shop Skin Shield Baby Cream or on Amazon UK for UK customers.

The Naturally Kind Co. It Really Works.