What Causes Hives (Urticaria)?

Medically reviewed by William Truswell, MD

Hives (urticaria) causes and risk factors include allergens, exposure to insect venom, medication side effects, or certain infections. Most chronic hives, which last more than six months, are idiopathic. This means hives has no known cause. Some cases of hives can be inducible, meaning environmental factors like heat, cold, water, or sweating trigger them.

Urticaria is an inflammatory skin disorder that causes itchiness and red or skin-colored bumps called wheals. Hives may occur as larger patches of swelling (angioedema). Having hives is a sign your immune system and skin are reacting to a sensitivity, allergen, irritant, or infection.

Related: What Is Stinging Nettle Rash?

Infections

The most common causes of hives are viral, bacterial, or parasitic infections, particularly in infants and young children. Infections can trigger your immune system into action, leading to urticaria flares. More research is needed to understand how.

The most common viruses that cause hives include:

• Epstein-Barr virus (EBV): Can cause mononucleosis (mono)

• Hepatitis A, B, or C viruses (HAV, HBV, or HCV): Affect the liver

• Herpes simplex virus (HSV), known as herpes: Causes sores on the mouth, lips, or genitals

• Human immunodeficiency virus (HIV): Affects the immune system and can lead to acquired immunodeficiency syndrome (AIDS)

• Rhinovirus: Commonly causes the common cold

• Rotavirus: Results in gastroenteritis, or the "stomach flu"

Hives may also arise due to bacterial infections. Cases have been linked to:

• Helicobacter pylori: Causes stomach infections

• Streptococcus: Commonly causes strep throat and skin infections called cellulitis

• Mycoplasma: Results in respiratory infections

• Urinary tract infections (UTIs): Affect any part of the urinary system and can result from different types of bacteria

Chronic urticaria has also been linked to different diseases caused by parasites. These microscopic organisms survive off other organisms. A parasite can enter your body when you drink contaminated water, come into contact with fecal matter, or through other environments.

Some parasitic infections that can trigger hives include:

• Anisakiasis: Caused by Anisakid parasites, often found in raw fish or squid

• Ascariasis: Caused by Ascaris parasites, usually found in soil or feces

• Giardiasis: Caused by Giardia parasites, often found in water

• Toxocariasis: Caused by Toxocara parasites, commonly found in dogs or cats

Allergens

Urticaria can occur during an allergic reaction. An allergic reaction arises when your immune system misreads an allergen, usually a harmless substance, as an invader. Your immune system then attacks the allergen using an antibody (a blood protein) called immunoglobulin E (IgE). This type of allergic reaction is called an IgE-mediated response and often happens almost right away after coming into contact with an allergen.

Allergens that may trigger an IgE-mediated response and lead to hives include:

• Bites or stings from bed bugs, bees, wasps, hornets, and fire ants

• Certain foods (e.g., eggs, milk, peanuts, soy, and wheat)

• Latex (e.g., some gloves, balloons, and condoms)

• Physical contact with certain plants, raw fruits, and vegetables

• Pollen, mold, or dust mites

• Some antibiotics (e.g., penicillin and cephalosporins)

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)

Nonsteroidal anti-inflammatory drugs (NSAIDs) are common medications that reduce pain and inflammation. Some types include Advil (ibuprofen), Bayer (aspirin), and Aleve (naproxen).

Some people who take NSAIDs may have an IgE-mediated response. Others may have pharmacologic reactions. These pseudo-allergic reactions don't involve IgE antibodies but still cause inflammation. You can develop hives within minutes of taking NSAIDs in either case. Some pharmacologic reactions can lead to hives one to two hours later.

Direct Effects of Drugs

Certain medications and plant chemicals can trigger inflammatory skin reactions in some people. Your immune system reacts using mast cells, or a type of white blood cell in your skin cells and other body parts. This allergic reaction is known as direct mast cell activation, which is not IgE-mediated.

Hives, swelling, and other allergic symptoms can develop anywhere from a few minutes to hours after exposure to the drug or substance. The timing can vary depending on whether you take the drug as a pill or intravenously or if the contact was through touch.

This reaction can occur with:

• Muscle relaxers like Tacrium (atracurium) and Norcuron (vecuronium)

• Opiate drugs (e.g., morphine, codeine, and dextromethorphan, or an opiate derivative in some cough syrups)

• Stinging nettle (Urtica dioica), which is a plant

• Vancomycin, which is an antibiotic

Environmental Triggers

Some people can develop hives when their skin is exposed to certain environmental or physical factors. This is called inducible urticaria, or physical urticaria, which occurs in up to 30% of adults with chronic hives. About 1% of adults have chronic hives.

People with inducible urticaria often have a health condition that makes their skin hypersensitive to a certain trigger. Some triggers and their related conditions include:

• Cold: Cold urticaria

• Direct sunlight or ultraviolet (UV) light: Solar urticaria, polymorphic light eruption (PMLE), and other photodermatoses (photosensitive conditions)

• Heat: Heat urticaria

• Pressure on the skin: Delayed-pressure urticaria or angioedema

• Sweat: Cholinergic urticaria

• Vibration: Vibratory angioedema and urticaria

• Water: Aquagenic urticaria
  

Is Hives Hereditary?

Research has found that some types of hives can happen in people with a genetic predisposition. Studies on identical twins and their shared urticaria (compared with fraternal twins, who don't have identical DNA) support this theory. Other evidence suggests that certain gene variants (genetic polymorphisms) can increase someone's susceptibility to acute urticaria triggered by NSAIDs.

There may be a hereditary factor. About 25% of people with chronic spontaneous urticaria had a family history of the same condition.

A rare form of cold urticaria is also hereditary, caused by an autosomal dominant mutation on a chromosome. If your parent carries at least one copy of the mutation, you have a 50% chance of developing the condition.

Who Gets Hives?

Some people are more likely to develop hives than others. This can vary by:

• Age: Children aged 5 and younger experience acute urticaria at a higher rate than others. Adults older than 30 are more likely to experience chronic hives.

• Ethnicity or race: All ethnicities can develop hives. Black and Latino people may experience urticaria at a higher rate than White people. Socioeconomic differences and environmental factors may play a role.

• Sex assigned at birth: Women are more likely to experience chronic hives than men. Women older than 30 have the highest rate of chronic spontaneous urticaria, which has no known cause.

Risk Factors

Certain diseases increase the risk of acute and chronic hives. Geography and economic status can also raise your chances of developing urticaria.

Geography

Where you live can serve as a risk factor. Living in areas with higher population density, for example, may increase the risk of urticaria.  Higher altitudes and areas with high temperatures can also trigger urticaria.

Economic Status

Research has shown that poverty and low socioeconomic status increase the risk of acute urticaria. High socioeconomic status serves as a risk factor for chronic hives.

Other Conditions

Living with or having a history of certain health conditions may increase the risk of hives. Some evidence suggests that women with peptic ulcer disease or abnormal uterine bleeding may have an increased risk for chronic urticaria. Peptic ulcer disease causes acid in the digestive tract that damages the inside of the stomach or small intestine.

Spontaneous urticaria, or idiopathic urticaria, is a type of hives with no identifiable trigger. Some spontaneous hives have been linked to certain diseases, but more research is needed. These include:

• Allergic diseases: A study published in 2019 of over one million 16-year-olds found that those with chronic spontaneous hives were more likely to have allergic diseases. These included food allergy, allergic rhinitis (hay fever), atopic dermatitis (eczema), and asthma.

• Autoimmune disorders: Research has found links between spontaneous hives and autoimmune disorders, or when the immune system mistakenly attacks the body. These autoimmune disorders include celiac disease, Sjögren’s syndrome, systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and type 1 diabetes.

• Thyroid disorders: Both underactive (hypothyroidism) and overactive (hyperthyroidism) thyroid disorders have been linked to spontaneous hives. The thyroid is a butterfly-shaped gland in the center of your neck.

Related: What Is Heat Rash?

A Quick Review

Urticaria is an inflammatory skin disorder that causes itchy hives to form on the body, along with swelling in some cases. Hives can happen in some people due to exposure to allergens, infections, and taking certain medications.

Hives can affect anyone, but children are more likely to develop acute urticaria. Urticaria also tends to be more common in women than men. You may have a greater risk of hives if you have certain health conditions, low socioeconomic status, and live in densely populated areas.

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