What Causes Hives?

QUESTION: This may seem like a trivial question, compared to some you answer,
but I hope you will devote some space to it. What causes hives?
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ANSWER: It's not a trivial question at all, as you will see. Hives,
technically termed urticaria, can be caused by a wide variety of factors that
involve either internal or external conditions. In many cases, the triggering
agent can remain elusive, but fortunately, hives usually clear up within a few
days and leave no evidence of damage to the skin. Furthermore, there are many
medications currently available that help control the symptoms.
Drug allergies are one possible cause of hives, with penicillin being the
most common agent. Hives will usually occur within thirty minutes of the
initial dose, making the source identification fairly simple. However, drugs
that cross-react with penicillin can delay the onset of a hives outbreak and
patients can frequently develop an allergic reaction to a drug whose prior
exposure did not cause a reaction, thus making positive drug identifications
quite complicated.
Aspirin is another drug that causes hives, though it is frequently
overlooked because patients rarely think to mention it when questioned about
medications they may be taking. Drug additives, such as sulfites that are
used as stabilizers in many liquid medications, can also trigger hives. And,
in some cases, patients can develop a hypersensitivity to an allergy shot
antigen which will result in hives as well.
Skin sensitivity is another source of hive outbreaks. After a walk in a
field, allergens such as pollen can penetrate the skin's surface and cause
welts. The licking or scratching of the skin by a pet can cause hives as
well. Sensitivity to certain materials, such as rubber gloves, can create
local reactions, as can touching certain foods like raw shellfish which may
cause no reaction when eaten in a cooked form. In most cases where skin
sensitivity is the culprit, the hives will develop within minutes and resolve
in a few hours.
Food allergies are yet another common link to hives. Peanuts, fish,
shellfish, milk, and eggs are the most common offenders, and usually produce
additional symptoms such as an itching in the mouth, a swelling in the throat,
cramps, diarrhea, and vomiting which make identification readily obvious.
However, in cases where the food allergy is not clear, testing should be done
before limiting a patient's diet unnecessarily.
Certain external factors can contribute to hive outbreaks as well.
Friction from tight clothing can trigger hives to develop along lines of
pressure, as can sudden exposure to cold air or water. Sweating induced by
heat, exercise, or anxiety can also produce skin lesions.
Whatever the cause, treatment for hives is readily available. Avoiding
offending food or drugs will usually prevent repeat attacks, but in chronic
cases, a daily antihistamine or corticosteroid may be advised. Patients
suffering from hive attacks should still bear in mind that even though the
condition is a puzzling one, it is not permanently damaging.
Sometimes the most elementary questions have complicated answers, and
common problems, like hives, have enormous implications to our health and well
being. That's why I never mind researching out even the simplest questions
you ask.