irritants

Irritants are harmful chemical or physical agents with a direct damaging effect on the skin after single or repeated application. They may have cytotoxic effects on epidermal cells, remove surface lipids, denature epidermal keratins or damage cell membranes. One major context for contact with irritants is occupational exposure.

The following substances act as potent irritants and cause skin lesions after one single application:
concentrated acids
concentrated alkali solutions
strong solvents

These substances are mild irritants, requiring repeated contact to induce skin lesions:
water
soap
detergents
oils/ greases
weak solvents

Several ingredients in cosmetics may also cause irritation.
Detergents in skin cleansing products may lead to dry skin and scaling.
Certain moisturisers, ingredients in sun tan lotions and perfumes in cosmetics may lead to stinging and itching. Propylene glycol and butylene glycol are typical triggers for stinging sensations.
Other potentially irritating ingredients in skin care products are formaldehyde, sodium lauryl sulfate, urea, balsam of Peru and derivates of cinnamon acid.