In biology, an irritant is anything that causes irritation such as inflammation or pain. This may be chemical in nature, but it can also be mechanical, thermal, or radiative. Chemicals like the capsaicin in hot peppers, rough fabrics, friction, heat or coldness, and ultraviolet (UV) radiation are all examples of irritants. Irritants commonly affect the skin, eyes, or mucous membranes.
The Occupational Health and Safety Administration (OSHA) defines an irritant as having a temporary and local effect. Contact with irritants can sometimes be avoided by wearing protective gear such as goggles or gloves, and the first line of treatment against irritants is typically flushing the affected area with water. If irritation persists, a doctor should be consulted. Though irritation is a temporary problem, some irritants can cause more long-term damage.
Irritants are not the same as allergens, though the two may overlap. Allergens cause an immune response, while irritants cause irritation through abrasion or by removing moisture from the affected area. The effects of irritants are limited, at least initially, to the area in direct contact with them, while an allergen can have more widespread or systemic effects. Finally, a certain amount of an irritant is required to have an effect, while allergens can typically cause a reaction in much smaller amounts.
One possible effect of contact with irritants is a condition such as eczema or irritant contact dermatitis (ICD), which affects the skin. Symptoms can include redness, rash, blisters, itching, swelling, dryness, and scaling. Many different factors contribute to the severity and duration of irritant contact eczema. These include the duration and frequency of contact with the irritant, the irritant's strength and amount, the sensitivity of the sufferer's skin, and environmental factors.
ICD can affect anyone, though those with atopic dermatitis and those who frequently handle irritants as part of their job are most susceptible. Young children can develop ICD around the mouth from dribbling or licking their lips frequently. Also, many people develop the condition in the winter as a result of cold, dry air.
When allergy is ruled out, ICD can be treated with compresses, emollient creams, and sometimes topical steroids or antibiotics for secondary infections. The patient should avoid contact with the irritant whenever possible, and should keep the affected area clean and moisturized. The skin can develop tolerance to some irritants over time.