Hives, also known medically as urticaria, are characterized by itchy bumps and raised patches on the skin. These unwelcome skin eruptions appear when your body releases histamine. Histamine is a chemical stored within your cells, and it plays a critical role in your immune response. When your immune system perceives a threat—whether it’s a genuine danger like an infection or something harmless like pollen—it releases histamine along with other chemicals. This release is intended to protect you from harm, such as infections, spoiled food, or insect bites.
However, sometimes the immune system mistakenly releases histamine even when there’s no actual threat. This misstep often occurs during an allergic reaction, and for many individuals, hives are a telltale sign of such a reaction.
Allergic Reactions: A Common Pathway to Hives
When hives arise due to an allergic response, it signifies that your body is overreacting to a substance it perceives as harmful. This substance, known as an allergen, can trigger the release of histamine, leading to the development of hives. Common allergens that can cause hives include:
- Foods: Certain foods like peanuts, shellfish, eggs, and milk are notorious for triggering allergic reactions and hives in susceptible individuals.
- Insect Bites and Stings: Venom from insect bites or stings, such as those from bees, wasps, or mosquitoes, can introduce allergens into your system, resulting in hives.
- Latex: Products made from natural rubber latex, like gloves or balloons, can cause allergic reactions in some people, manifesting as hives.
- Medications: A variety of medications, including antibiotics (like penicillin) and nonsteroidal anti-inflammatory drugs (NSAIDs), can provoke allergic reactions and hives.
- Pet Dander: Proteins found in animal skin, saliva, or urine, commonly known as pet dander, are a frequent allergen for many, leading to hives among other allergic symptoms.
- Plants: Contact with certain plants, such as poison ivy, poison oak, or poison sumac, can cause allergic contact dermatitis, which may include hives.
- Pollen: Airborne pollen from trees, grasses, and weeds is a seasonal allergen that can trigger allergic rhinitis and, in some cases, hives.
Beyond allergic reactions, hives can also be triggered by non-allergic factors, indicating that the histamine release is not due to a typical allergic response. These triggers include:
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Physical Stimuli:
- Heat and Sweat: Overheating or excessive sweating can sometimes provoke hives in certain individuals, known as cholinergic urticaria.
- Cold: Exposure to cold temperatures, including cold air or water, can induce cold urticaria, a type of hives.
- Sunlight: For some, direct sunlight exposure can lead to solar urticaria, a form of hives triggered by UV radiation.
- Pressure on the Skin: Physical pressure or friction on the skin, such as from tight clothing, scratching, or even the pressure of a purse strap, can cause pressure urticaria.
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Stress: Emotional or physical stress can sometimes act as a trigger for hives in susceptible individuals, although the exact mechanism is not fully understood.
Infections and Medical Treatments as Hives Triggers
Infections and certain medical procedures can also prompt the development of hives. This occurs as the body’s immune system responds to the infection or treatment.
- Infections: Viral, bacterial, and fungal infections can all potentially trigger hives. Common infections associated with hives include:
- Strep throat
- Urinary tract infections (UTIs)
- COVID-19
Hives as an Early Sign of COVID-19
In some instances, hives can be one of the initial symptoms of COVID-19, even preceding more common symptoms like fever and cough.
- Medical Treatments: Certain medical interventions can also lead to hives as a side effect. These include:
- Radiation Therapy: Radiation therapy, while crucial for cancer treatment, can sometimes cause skin reactions, including hives, as the body reacts to the treatment.
- Blood Transfusions: In rare cases, individuals may develop hives as a reaction to blood transfusions.
Hives as a Reaction to Radiation Therapy
The Mystery of Unidentified Hives Triggers and Chronic Spontaneous Urticaria
For many people who experience hives, pinpointing the exact trigger remains elusive. It’s estimated that a significant portion of individuals who develop hives will never identify the underlying cause. In some cases, hives become a persistent issue, lasting for six weeks or longer. This condition is known as chronic spontaneous urticaria (CSU).
Urticaria is the medical term for hives, and when it becomes chronic and spontaneous, it means the hives appear repeatedly over an extended period without a clear external trigger. Chronic spontaneous urticaria can significantly impact quality of life due to the recurring discomfort, itching, and swelling.
Interestingly, women are about twice as likely as men to develop chronic spontaneous urticaria, with onset often occurring between the ages of 20 and 40.
Risk Factors Increasing Susceptibility to Hives
While hives can affect anyone, certain factors can increase your risk of developing them:
- Race and Ethnicity: Studies indicate that women of African American heritage have a significantly higher risk (4 to 5 times greater) of developing hives compared to white individuals.
- Atopic Dermatitis (Eczema): Individuals with atopic dermatitis, a chronic inflammatory skin condition, are more prone to developing hives.
- Smoking: Cigarette smoking has been identified as a risk factor for hives.
If you are experiencing hives that are widespread, long-lasting, or if you are unsure whether you have hives, consulting a dermatologist is advisable. A dermatologist can accurately diagnose your condition and recommend appropriate treatment strategies to help you manage your symptoms and improve your skin health. For more information on diagnosis and treatment, you can refer to Hives: Diagnosis and treatment.
Images Image 1: Used with permission of the American Academy of Dermatology National Library of Dermatologic Teaching Slides.
Image 2: Images used with permission of JAAD Case Reports.
- JAAD Case Reports 2021;11:137-8.
Image 3. Image used with permission of the Journal of the American Academy of Dermatology.
- J Am Acad Dermatol 2006;54(1)28-46.
References Antia C, Baquerizo K, et al. “Urticaria: A comprehensive review: Epidemiology, diagnosis, and work-up.” J Am Acad Dermatol. 2018;79(4):599-614.
Grattan CEH, Saini SS. “Urticaria and angioedema.” In: Bolognia JL, et al. Dermatology. (4th edition). Mosby Elsevier, China, 2018:304-19.
Hide M, Takahagi S, et al. “Urticaria and angioedema.” In: Kang S, et al. Fitzpatrick’s Dermatology. (9th edition) McGraw Hill Education, United States of America, 2019:684-785.
Hymes SR, Strom EA, et al. “Radiation dermatitis: Clinical presentation, pathophysiology, and treatment.” 2006. J Am Acad Dermatol. 2006;54(1):28-46.
Le NK, Brooks JP. “Acute urticaria as the initial presentation of COVID-19 in a pediatric patient.” JAAD Case Rep. 2021;11:137-8.
Rosman Y, Hershko AY, et al. “Characterization of chronic urticaria and associated conditions in a large population of adolescents.” J Am Acad Dermatol. 2019;81(1):129-135.
Written by: Paula Ludmann, MS
Reviewed by: DiAnne Davis, MD, FAAD Elisa Gallo, MD, FAAD William Warren Kwan, MD, FAAD Shari Lipner, MD, PhD, FAAD
Last reviewed: 5/30/24
