With this type of hives, the cause can usually be found. The most common causes are foods, drugs, or infections. Insect bites and internal disease may also be responsible. Other causes can be pressure, cold, or sunlight. The most common foods that cause hives are nuts, chocolate, fish, tomatoes, eggs, fresh berries, and milk.
Fresh foods cause hives more often than cooked foods.
Food additives and preservatives may also cause hives. Hives may appear within minutes or up to two hours after eating, depending on where the food is absorbed in the digestive tract. Diet supplements, antacids, arthritis medication, vitamins, eye and eardrops, laxatives, vaginal douches, or any other non-prescription item can be a potential cause of hives. If you have an attack of hives, it's important to tell your doctor about all of the preparations that you use to assist in finding the cause. Many infections can cause hives.