Hives are raised red bumps (welts) or splotches on the skin. They’re a type of swelling on the surface of your skin and happen when your body has an allergic reaction. Allergic reactions happen when your immune system comes in contact with an allergen. Allergens are proteins that are harmless to many people but cause an allergic reaction in sensitive people.
Hives are often very itchy, but you might also feel burning or stinging. They can be as small as a fingertip or as big as a dinner plate. The medical name for hives is urticaria.Sometimes, the welts from hives join together to form larger areas called plaques. Hives tend to fade within 24 hours, although they may be noticeable for several days or longer.
Types of hives
Acute urticaria refers to hives that don’t last very long (less than six weeks). Chronic urticaria refers to hives that happen at least twice a week for more than six weeks. Chronic, spontaneous urticaria is the name for chronic hives that don’t have an obvious cause. An older name for this condition is chronic idiopathic urticaria. There’s also a condition called physical urticaria, or inducible urticaria. These hives might pop up when you’re in the cold, heat or sun. Some people react to vibrations or pressure, exercising or sweating. Physical hives usually appear within an hour after exposure. This type of hives can also be chronic.
Symptoms of acute hives:
Hives look different depending on the person and the situation. They can show up anywhere on your body. Signs of acute hives include:
- Raised welts or bumps on your skin. The bumps may look reddish on lighter-coloured skin.
- Hives blanch (the centre of the hive becomes pale when pressed).
- Itchy skin.
- Swelling under your skin causing puffiness (angioedema).
- Also appearing with painful swelling of your lips, eyes and inside your throat.
Symptoms of chronic hives:
In many respects, chronic hives and acute hives may look alike: they can be itchy, swollen raised welts that turn lighter in the centre and with pressure. However, chronic hives can:
- Shift sizes and shapes.
- Appear, disappear and then reappear at least every few days for long periods of time, even months or years.
- Happen along with heat, exercise or stress.
Causes of acute hives:
Acute hives are often an allergic reaction to something you put into your body, like food, drink or medication, or something that you touch. The skin has immune cells called mast cells. When these cells go into action, they release chemicals, including one called histamine. Histamine is the reason that hives form.
You can also get hives for a variety of other reasons. Some of these include having an infection, stress or physical pressure on your skin. It’s not uncommon for healthcare providers to be unable to determine exactly what caused your hives.
Causes of chronic hives:
Unlike acute hives, chronic hives aren’t usually caused by allergies. They may be caused by infections from bacteria or viruses, or as a result of other medical conditions like lupus. Your provider may not discover an exact cause. In these cases, chronic hives are said to be idiopathic or spontaneous. Chronic hives do last for long periods of time but usually aren’t permanent. They can be uncomfortable, but they aren’t life-threatening.
