January 09 : Some chemicals found in creams and cosmetics may cause a skin rash, reveals a new study. These compounds harm the natural molecules called lipids in our skin cells and cause allergic reactions.
A new study conducted by Columbia University Irving Medical Center, Brigham and Women's Hospital, and Monash University, suggests that common ingredients found in cosmetics trigger allergic contact dermatitis, which are harmful to our skin.
Why some chemicals trigger skin rashes
It is still a mystery why some chemicals trigger dermatitis. For example, poison ivy is an itchy rash that is caused by an allergic reaction to an oily resin called urushiol. This oil is found in the poison ivy plant. Researchers have pointed out that many non-prescribed ingredients found in topical products can cause a similar rash.
When the immune system's T cells recognise a chemical as foreign, our skin becomes allergic to it. However, it is surprising that T cells do not directly recognise these small chemicals as foreign. When these compounds react with larger proteins, it is visible to the T cells.
The study surprisingly found that the chemical groups that are needed in compounds to be visible to T cells may be missing, yet they are visible to T cells and, therefore, trigger allergic reactions.
The researchers believe that CD1a, a molecule that is found on immune cells on the skin's outer layer called Langerhans cells, may be responsible for making these chemical compounds visible to T cells.
The study also found that several common chemicals that trigger skin rash can bind with CD1a molecules on the surface of Langerhans cells, and hence, activate T cells.
Some of these common chemicals are Balsam of Peru and farnesol found in consumer products like creams, toothpaste, and fragrances. The researchers found that benzyl benzoate and benzyl cinnamate in Balsam of Peru are responsible for the reactions. These chemicals activate T cells.
The researchers found that CD1a molecules bind with the skin's lipids in its tunnel-like interior. When these lipids extend beyond the tunnel, they create a barrier that prevents CD1a from interacting with T cells.
The new study found that farnesol, one of the common allergens, can hide inside the tunnel of CD1a and displace the lipids that extend beyond the CD1a molecule. This displacement makes the CD1a visible to the T cells.
A new way to treat the condition
This revelation led to a possible solution. If allergic contact dermatitis is stopped by applying competing lipids to the skin, it can displace those that trigger the reaction. The researchers suggest that the only way to treat skin rash from these chemicals is to identify the allergic contact dermatitis and stop their contact with the reacting chemicals.