The allergic sensitization may remain with the individual through life. If there is no further contact with the allergen, the level of sensitivity may gradually decline. Cuts or scratches, into which allergenic substances can enter, also contribute to the development of allergic contact dermatitis. Important individual factors include the resistance of the skin, which increases with age. Hereditary factors influence the variety of reactions in different persons exposed to the same allergen.
Environmental factors play a significant role.
For example, hot workplaces cause sweating, which can dissolve some types of industrial chemical powders, increasing their toxicity for the skin. Dry air can cause chapping of the skin, increasing the possibility of allergies. This can diminish the protective action of skin against allergens. Some of the occupations where allergic contact dermatitis has been seen are listed in the following tables. Some industrial substances which can cause allergic contact dermatitis may not be listed.