This is a skin reaction medically known as urticaria that causes itchy welts on the skin to develop when the body releases histamine. They can be caused by:
- An allergic reaction
- A physical trigger, such as cold, water, or pressure
- A medical condition, such as an infection or autoimmune disease
It can be helpful to see a board-certified dermatologist if the hives:
- Last longer than a few days
- Cover a large area of your body
- Are caused by an allergy
Your body stores histamine inside cells. When your immune system recognizes a threat, it releases histamine and other chemicals. This cascade of chemicals can protect you from becoming seriously ill from an infection, spoiled fish, or a bug bite.
Sometimes, the immune system releases histamine when there is no real threat. This happens when people develop an allergic reaction. In fact, some people develop hives when they have an allergic reaction.
When the body mistakenly releases histamine and hives develop, the cause is often one of the following:
- An allergic reaction
- Overreaction to heat, sweat, or cold
- Pressure on the skin (tight clothing, light touch of a purse strap, or scratching)
When hives are due to an allergic reaction, it’s often an allergy to:
- A food
- Bug bite or sting
- Pet dander
Some people get hives when they develop an infection like strep throat, a urinary tract infection, or COVID-19. Others get hives when they have a medical treatment like radiation therapy or a blood transfusion. While some people can trace hives back to a trigger like an allergic reaction, exposure to cold, or stress, the cause remains a mystery for many people.
For some people, the cause of their hives is something that touches their skin. Your own sweat, cold, sunlight, or the light pressure of a purse strap can cause hives. Dermatologists call this type of hives inducible hives. It only develops when something that causes hives for that person touches the skin.
When this type of hives continues for six weeks or longer, it’s called chronic inducible hives. By avoiding the cause, you can prevent new hives.
Hives can develop anywhere on your skin. If you have hives, they may appear in one area like your back or cover much of your skin. For most people, hives appear on one or more of these areas:
- Upper arms
- Upper legs
Hives can also develop on soft, moist tissue that lines your eyelids, mouth, and other areas. Some people also develop swelling deep in their skin. Hives cause inflammation in the skin, so the skin may feel hot and swollen. Some people who get hives also develop another type of swelling that occurs deep in the skin or moist tissue that lines the lips, mouth, inside of the eyelids, and elsewhere. This swelling is called angioedema. It tends to cause pain rather than itch.
Hives may appear as bumps, raised patches, or both that suddenly appear on the skin. The bumps and raised patches are often itchy and may look swollen. These welts, also called wheals, may be red, pink, white, or skin-colored. Just as they vary in color, hives come in many shapes. Some appear as tiny spots or blotches. Others look like thin, raised lines. The size of an individual hive ranges from as small as a pinhead to several inches across. Hives can appear alone or in a group. Some hives join to form large patches called plaques. They are usually harmless and temporary.
A single hive tends to last for a few minutes to a few hours. Most hives clear within 24 hours. As existing hives clear, new ones can form. New hives may appear on the same or different areas on the skin. Most people get new hives for a few days to a few weeks. If you continue to get hives daily or almost every day for six weeks or longer, you have chronic hives. The medical term for this is “chronic urticaria."
It’s estimated that millions of people in the United States will develop hives during their lifetime and never find the cause. Some of these people will continue to have hives for six weeks or longer. When this happens, the person has a medical condition called chronic spontaneous urticaria (CSU). With CSU, hives can continue to appear for months and sometimes years. During this time, the swelling, pain, and discomfort can be difficult to live with. Women are twice as likely as men to develop CSU in their lifetime and is usually seen in women of ages 20 to 40 years old.
If you have long-lasting or widespread hives, seeing a dermatologist can help you feel more comfortable. Seeing a dermatologist is also a good idea to make sure that what you have really is hives.
If you have a mild case of hives, it will likely go away in a few days. To get relief until then, dermatologists recommend that you take a non-drowsy antihistamine.
Even without knowing the cause, your dermatologist can treat hives. When treating hives, the goals are to:
- Control the itch
- Prevent new hives (existing hives go away on their own)
- Avoid what’s causing the hives (when known)
Your treatment plan will be tailored to your needs and may include one or more of the following:
- Soothing anti-itch lotion or cream
- An antihistamine
- Light therapy
- Other medication as needed
Most hives go away on their own in a few days or weeks. During this time, you can often relieve the itch and discomfort at home with these tips from board-certified dermatologists.