Foods and additives like Milk, egg, peanuts, nuts, soy, and wheat are the most common agents to cause such dermatitis. Also allergens which should not be neglected are fragrances (perfume,
cosmetics), preservatives (topical medications, cosmetics), rubber etc.
This triggering factor should be identified and should be avoided. And even a skin allergy test can be useful.
You can try anti histaminics against prescription, but prevention is the best cure.