Hives – also called urticaria – are localized, raised red areas in the superficial portion of the skin that may join together to form larger lesions. Hives are closely related to angioedema.
Incidence; Causes and DevelopmentHives
are relatively common with at least 20% of the population having had at least one episode during their lifetime. Although seen in all ages, they seem to be more prevalent among young adults.
The reaction involves the release of histamine
from either mast cells
causing an IgE
(immediate type) mediated antibody
The causes of urticaria
are many and in 80% of cases never determined; not knowing the cause often results in an on-going problem. The most common causes of chronic urticaria are drug reactions, stress, food sensitivities and fungal infections. Some initiating factors include:
- Allergic urticaria: plants, pollens, drugs (including aspirin), foods (such as shellfish, eggs, nuts, strawberries, certain baked goods) and food additives, animal dander, cosmetics, toxins from jellyfish, caterpillars or fleas, "contactants" such as latex (especially in health care workers).
- Physical urticaria: heat or sun, cold, light, pressure from bracelets and clothes or scratching, vibration, exercise
- Secondary urticaria: infections (e.g. hepatitis B virus, candida albicans, streptococcal bacteria), collagen vascular diseases, autoimmune diseases or other metabolic disorders, cancer, psychological, hypothyroidism, polycythemia vera, protoporphyria (even without excessive sun exposure). Mechanical, physical or emotional factors might play a role.
Signs and Symptoms
Itching is usually the first symptom. The wheals
are white or red, occasionally with a pale center. Plaques are developed by 50% of patients and the lesions
often come and go in different areas.
Diagnosis and Tests
Lab findings are often unremarkable in cases of acute urticaria
. For chronic urticaria, lab work should include CBC
, ESR, UA, histamine
levels and dental/sinus
examinations to rule out hidden pathology.
Treatment and Prevention
Instead of just treating the symptoms (which is obviously important as well), a physician needs to get the the bottom (if there is one) of why the patient is getting them in the first place.
lasts from 1 to 7 days and treatment is not usually needed except to reduce the itching. The inciting agent must be dealt with, be it food, external agent or an emotion. In severe cases, epinephrine
, as found in a bee sting kit, may be required.
In cases of chronic urticaria
of over three weeks' duration, 50% of patients experience spontaneous remission within two years, even though in the majority of cases the cause is never identified.
In extreme cases, swelling in the throat may lead to a medical emergency.