What is hives?

Hives are bumps, like red hives or welts, that stand out on the skin. Hives are a common skin reaction to something like an allergen (a substance that causes allergies).

Hives can appear anywhere on the body, both as tiny pimples, spots, or large, interconnected bumps.

Each bump or bump can last from a few hours to a week (and sometimes longer), and new bumps or bumps appear to replace those that are disappearing. Hives that last 6 weeks or less are called acute hives; hives that last more than 6 weeks are called chronic urticaria.

Causes of hives

An allergic reaction can cause hives, and can also be caused by:

  • extreme temperatures
  • stress
  • infections
  • some diseases

In some cases, people develop hives and angioedema, a condition that causes swelling around the eyes, lips, hands, feet, or throat. Very rarely, hives and angioedema are associated with an allergic reaction that affects the whole body, or anaphylactic shock .

Hives or red hives appear when mast cells in the bloodstream secrete a chemical called histamine, causing the tiny blood vessels under the skin to leak. Fluid collects inside the skin and forms large pimples and / or hives. This can happen for a number of reasons. But, in many cases, the cause is not identified.

Most often, hives are caused by an allergic reaction; which can cause the skin to become covered in hives within minutes after exposure to the allergen. Common allergies include the following:

  • to foods, especially shellfish , peanuts , tree nuts, milk and fruit.
  • to medicines (antibiotics) and allergy shots
  • pets and other animals
  • pollen
  • to insect bites and stings

Sometimes outbreaks of hives are not related to allergies. Other causes of hives include the following:

  • infections, including those caused by viruses
  • physical exercise
  • anxiety or stress
  • sun exposure
  • exposure to cold, such as immersing yourself in cold water or snow
  • contact with chemicals
  • scratching (dermographism)
  • exposing the skin to excessive pressure, such as sitting for a long time or carrying a heavy backpack slung over one shoulder.

Hives caused by physical causes (such as pressure, cold, or sun exposure) are known as physical hives.

Finding out what causes chronic hives can be difficult, although chronic hives are sometimes associated with diseases of the immune system, such as lupus . Other times, a drug, food, insects, or infection can trigger an outbreak of hives. However, doctors do not usually know the cause of chronic hives.

What are the signs and symptoms of hives?

The distinctive red bumps that protrude on the surface of the skin are the main sign of hives. May:

  • have a pale hue in the middle
  • appear grouped (or in clusters)
  • change shape and location in a matter of hours
  • be small or as big as a plate of food
  • itching, stinging, or burning

If hives occur along with angioedema, it may be associated with swelling, inflammation, red bumps, or large bumps around the eyes, lips, hands, feet, genitals, or throat. Other symptoms can be nausea, vomiting, and stomach pain.

Exceptionally, a person with hives and angioedema may have anaphylactic shock. Signs of anaphylactic shock include trouble breathing, low blood pressure (hypotension), dizziness, and / or loss of consciousness (fainting).

How is hives diagnosed?

Most of the time, doctors can diagnose hives simply by looking at the patient’s skin. To try to identify its cause, your doctor may ask you questions about your medical history: illnesses you have recently experienced, medications you take, your exposure to allergens, and the stressors you are subjected to each day.

If you have chronic hives, your doctor may ask you to keep a daily log of your activities, what you drink and eat, and where the hives tend to appear on your body. Your doctor may order diagnostic tests, such as blood tests, allergy tests, and other tests to rule out other conditions that could be causing your hives, such as thyroid disease or  hepatitis , in order to find out the exact cause of your hives.

To find out if you have physical hives, your doctor will ice your skin to see how it reacts to the cold, or hang a sandbag or other heavy object from your thighs to see if the pressure causes hives to appear on your skin.

How is hives treated?

Mild hives often go away on their own without the need for treatment. If a clear trigger for urticaria is identified, avoiding it as much as possible will be part of the treatment. If your hives are itchy, your doctor may recommend taking an antihistamine to stop your body from releasing histamine into your bloodstream to prevent further breakouts.

If you have chronic hives, your doctor may recommend an over-the-counter, non-drowsy antihistamine to take every day. However, not everyone responds the same way to medications, so it is important that you work with your doctor to find the one that is best for you.

If an antihistamine that doesn’t cause drowsiness doesn’t work, your doctor may recommend a stronger antihistamine, another drug, or a combination of drugs. In rare cases, your doctor may prescribe a steroid, in pill or syrup form, to treat chronic urticaria. This treatment is generally only prescribed for short periods of time (five days to two weeks), to avoid the harmful side effects of steroids.

In case of medical emergency

Anaphylactic shock and severe hives are very rare. But when they do occur, they require immediate medical attention.

People with severe allergies should always carry an epinephrine injection. If you are at risk for severe allergic reactions, your doctor will teach you how to give yourself an epinephrine injection safely.