So, why do hives occur? It turns out that there are many dif­fer­ent caus­es. For­tu­nate­ly, most cas­es are rel­a­tive­ly mild con­di­tions that are not life threat­en­ing. But, there are a few instances where urticaria, or the hives, rep­re­sents a seri­ous under­ly­ing med­ical condition.

One of the most com­mon­ly impli­cat­ed caus­es is an aller­gic reac­tion. Med­ica­tions, sting­ing insects, foods, food addi­tives, and cer­tain mate­ri­als that make con­tact with the skin are all known to cause hives. Although vir­tu­al­ly any med­i­cine can induce hives, the most com­mon drugs are antibi­otics, nar­cotics, anti-inflam­ma­to­ry agents (NSAIDs), mus­cle relax­ants, and radio­con­trast agents used for imag­ing studies.

Aller­gic reac­tions to food typ­i­cal­ly result in urticaria with­in 30 min­utes of inges­tion. Milk, eggs, toma­toes, peanuts, straw­ber­ries, tree nuts, soy, and wheat are some of the com­mon foods that affect young chil­dren. In old­er chil­dren and adults, fish and shell­fish are also a poten­tial cause.

Even though most of us asso­ciate hives with things that are ingest­ed, there are a few things that can induce them just by mak­ing con­tact with the skin. These sub­stances include cer­tain plants, raw fruits and veg­eta­bles, latex, and raw seafood. Con­tact with ani­mal sali­va, cold tem­per­a­tures, and heat (exer­cise, hot show­ers) are also com­mon causes. 

Despite the belief that aller­gies are the most com­mon cause of hives, infec­tions actu­al­ly account for up to 80% of all cas­es in chil­dren. Most of these infec­tions are self-lim­it­ed viral ill­ness­es that require no spe­cif­ic ther­a­py. Some bac­te­ria and even par­a­sites have also been known to cause hives.

Final­ly, hives may be part of a chron­ic under­ly­ing med­ical ill­ness. These sit­u­a­tions are rare and there are usu­al­ly oth­er signs and symp­toms present – fever, joint or mus­cle pains, weight changes, enlarged lymph nodes, fatigue, etc.

When should I be con­cerned about hives?

Urgent med­ical atten­tion should be sought when the rash is accom­pa­nied by such things as lip or tongue swelling, facial swelling, short­ness of breath, wheez­ing, abdom­i­nal pain, vom­it­ing, dizziness/​faint­ing, or pro­found weakness.

In the absence of oth­er seri­ous symp­toms, treat­ment is aimed most­ly at relief of the itch­ing. Anti­his­t­a­mine med­ica­tions are used most com­mon­ly and are avail­able over the counter. They are approved for rou­tine use in chil­dren over the age of 2 yrs. New­er anti­his­t­a­mines such as cet­i­rizine (Zyrtec), lora­ti­dine (Clar­itin), and fex­ofe­na­dine (Alle­gra) tend to be less sedat­ing and have the con­ve­nience of once or twice dai­ly dos­ing. Old­er anti­his­t­a­mines such as diphen­hy­dramine (Benadryl) are very effec­tive; how­ev­er, they are more sedat­ing and require mul­ti­ple dos­es per day.