Hives

What is hives?

Hives is a rash caused by an overload of the chemical histamine. The clinical name for this is urticaria. Hives can be acute and short-term, lasting less than six weeks, or recurrent and long-term.

Another type of hives, known as ‘urticaria vasculitis’, causes blood vessels within the skin to become inflamed. In this case, the rash can last longer than 24 hours and can be extremely painful and cause bruising of the skin.

Hives can be distressing and disrupt daily life and sleep. It’s important to see your doctor if your symptoms don’t improve within 48 hours.

Who gets hives?

Just about anyone can get hives, but people with allergies are more likely to develop it, usually when exposed to an allergen. It’s also more common in the 20-40 years age group, and twice as common in women.^[1]

Acute hives is also more common in adolescents and children, impacting about 3% of children, and in those with atopy (a tendency to develop allergic reactions due to an exaggerated immune response to common allergens).

How common is hives?

Hives is quite common, affecting up to 20% of the population over their lifetime.^[2] Hives is more common when you’re in your forties, though the peak age for getting it is between 20 to 40 years old.

What causes hives?

Acute hives usually develops in response to a trigger, like being exposed to something you’re allergic to, or by catching a viral infection like a cold or flu.

We don’t always know why chronic hives happens, but it’s often a combination of several factors. Hives occurs when something triggers the body to produce a high level of histamine, which is sent to the skin, causing your blood vessels to open up, swell, and itch.

Sometimes hives can be caused by an allergic reaction to particular foods, such as milk, eggs, or shellfish. Hives can also be triggered by reactions to insect bites, latex, particular drugs like penicillin, and vaccines. It can also appear in response to the skin coming into contact with something, like pressure or an irritant. Common examples include hot or cold water, sitting or lying down for long periods of time, and even wearing tight clothes.

What are the symptoms of hives?

The most common symptom of hives is a red and itchy rash. This rash can affect any area of skin on the body. Small areas, which are raised from the surface of the skin, look like blisters and cause itching. These areas are usually around 1-2cm (about 0.4-0.8 inches) across, but can vary from case to case.

Some people may experience a small cluster on one part of the body, but in other cases, rashes can appear on different parts of the body, and can be separate or join up to form bigger ones. They are often round, but can take other shapes as well.

Can hives lead to other problems?

Most people with hives don’t suffer from any other side effects. However, in some cases a condition called “angioedema” can appear at the same time as the hives. This condition causes fluid to leak into deeper tissue underneath the skin, causing it to swell. This swelling can appear anywhere on the body, but is more common on the lips, eyelids and genitals.

If you have hives, you should try not to scratch it. If you break the skin, you risk it becoming infected or forming a scar. Hives can be distracting or painful but most cases are mild. In severe cases, the tongue and throat can become swollen and can cause difficulty with breathing, which would need immediate medical attention.