What is homosalate?
Homosalate is a chemical sunscreen based on the naturally occurring molecule salicylic acid. Salicylic acid is found in willow plants but for industrial use it is typically made synthetically. Another molecule is stuck onto the salicylic acid to make it less soluble in water so the sunscreen doesn’t get washed off easily. It is good at absorbing UVB rays, however there are some concerns about it’s safety (see below)
Chemical sunscreens are one of two classes of sunscreen, the other being mineral sunscreens like titanium dioxide or zinc oxide.
Homosalate is also sometimes used in fragrances.
How does it work?
Sunscreens protect your skin from the sun’s harmful UV rays. When it hits your skin, UV light can enter your skin cells and damage their DNA. This DNA damage can cause mutations which can lead to cancer. Some wavelengths of UV called UVB directly damage the DNA while other wavelengths called UVA create reactive free radicals which attack the DNA. Your body tries to prevent these mutations progressing into cancer by triggering inflammation and sunburn. As well as being painful, this inflammation also damages the collagen in your skin, leading to wrinkled and aged looking skin.
When sunscreens like homosalate are applied to the skin, they create a protective barrier which absorbs UV light before it can get inside your skin cells. The salicylic acid part of homosalate is good at absorbing UVB rays and small amount of UVA. As chemical sunscreens have different wavelengths they’re best at absorbing, homosalate is usually mixed with a molecule that absorbs UVA well to increase protection.
There is some concern that once absorbed into the body (1% applied to the skin gets fully absorbed), homosalate is a weak endocrine disruptor – that is it can mess with your hormones by impersonating sex hormones like estrogen and androgen. This has only been seen so far in cell culture test, not in actual live human bodies so as it stands there isn’t solid evidence as to whether this hormone disruption problem is truly the case in humans.
There are also concerns that it may accumulate in the body.
Like many other chemical sunscreens, homosalate can trigger an allergic reaction in some people. This allergy might be in the form of photocontact dermatitis where the allergic reaction doesn’t trigger until the skin covered in homosalate is exposed to sunlight.
Homosalate may interact with Aminobenzoic acid, Benzocaine, Sulfa drugs and Tetracaine
Coppertone, Homomenthyl salicylate, 3,3,5-trimethylcyclohexyl salicylate, Heliopan, Filtersol A, Salicylic acid, m-homomenthyl ester