Allergens most often cause hives. In response to an allergic reaction from the chemicals in food, insect bites, sun exposure, and certain medications, blood vessels in the skin release histamine. As histamine works to remove the allergens from the body, the skin’s blood vessels can, in turn, release blood plasma that leads to hives.
No tests for hives exist. A dermatologist diagnoses the several types of hives based on the duration and severity of symptoms.
- Acute urticaria is a relatively severe case of hives that can result from an internal disease or a severe allergen. Foods that are known to cause acute urticaria include tomatoes, fish, milk, nuts, and food preservatives. Medications for pain relief and high-blood pressure are likewise allergens that can cause hives.
- Chronic urticaria is a case of hives that last for a minimum of six weeks. The causes of chronic urticaria are often challenging to identify, but certain diseases do correlate with this type of hives. The effects of chronic urticaria can also diminish the health of the lungs, gastrointestinal tract, and other internal organs.
- Dermatographism is a mild type of hives brought on by repeated and firm strokes or scratches to the skin. It may appear in conjunction with other types of hives as the result of persistent scratching of itchy skin.
Standard treatments for hives include antihistamines designed to reduce the trigger for the condition. Hives can also be managed by applying cold compresses and wearing loose-fitting clothes.