Hives

What Are Hives and What Causes Them?

Hives are pink welts or swellings that can itch, burn or sting. They vary in size and typically go away within 24 hours. If you have hives that last longer than this, see a board-certified dermatologist. Hives appear anywhere on the body, but swelling from hives usually happens around the eyes, lips or genitals. Swelling usually goes away within 24 hours though. In rare situations, hives can block your airway and obstruct breathing or swallowing. If you experience this, seek immediate emergency medical care.

Anyone can get hives, and typically they occur from allergic reaction to foods or medications. For children, the most common foods that cause hive breakouts are milk, eggs and peanuts. In adults, nuts, shellfish and eggs are the most common culprits. Fresh foods usually cause breakouts more than cooked foods. Food additives and preservatives can also be a cause. Almost any prescription or over-the-counter drug can cause hives. In addition, upper respiratory tract infections and colds can trigger hives, as can viral, bacterial and fungal infections.

There is the possibility for non-allergic hive breakouts. Narrowing down the exact cause can be difficult. 

Types of Hives

Acute Hives

These usually are the result of allergic reaction and appear quickly after eating certain foods or taking certain medications. They can also result from infection. Usually, these only last a few hours.

Chronic Hives

This causes multiple cases of hives over a period of time. These can also result from medications, infections or possible internal problems. Identifying the cause can be difficult, but bloodwork or biopsy may be helpful.

Physical Hives

This type of hives is caused by a physical factor(s) like heat, cold, sunlight, water, exercise, etc. 

• Dermatographic urticaria forms from rubbing or itching skin. This is the most common form of hives and appear within a few minutes of scratching, usually lasting less than an hour.
• Sun hives (solar urticaria) occur from sun exposure and typically fade one to two hours after getting out of the sun.
• Cold hives (cold urticaria) appear when the skin is warmed after prolonged cold, like when swimming. These can cause wheezing, flushing and fainting.
• Pressure hives can appear on parts of the body that are under pressure for extended periods of time, like at the top of the ankle where a sock band is tight. These can take hours to appear.