Many different substances in the environment may cause hives, including medications, food and physical agents. In perhaps more than 50% of people with chronic hives of unknown cause, it is due to an autoimmune reaction. Risk factors include having conditions such as hay fever or asthma. Medications
Drugs that have caused allergic reactions evidenced as hives include codeine, sulphate of morphia, dextroamphetamine, aspirin, ibuprofen, penicillin, clotrimazole, trichazole, sulfonamides, anticonvulsants, cefaclor, piracetam, vaccines, and antidiabetic drugs. The antidiabetic sulphonylurea glimepiride, in particular, has been documented to induce allergic reactions manifesting as hives. Food
The most common food allergies in adults are shellfish and nuts. The most common food allergies in children are shellfish, nuts, eggs, wheat, and soy. One study showed Balsam of Peru, which is in many processed foods, to be the most common cause of immediate contact urticaria. Another food allergy that can cause hives is alpha-gal allergy, which may cause sensitivity to milk and red meat. A less common cause is exposure to certain bacteria, such as Streptococcus species or possibly Helicobacter pylori. Infection or environmental agent
Hives including chronic spontaneous hives can be a complication and symptom of a parasitic infection, such as blastocystosis and strongyloidiasis among others.The rash that develops from poison ivy, poison oak, and poison sumac contact is commonly mistaken for urticaria. This rash is caused by contact with urushiol and results in a form of contact dermatitis called urushiol-induced contact dermatitis.
A number of children diagnosed with the disorder have been born to parents who were first cousins. It can also be associated with uniparental isodisomy. Diagnosis
Treatment
Epidemiology
Fumarase deficiency is extremely rare - until around 1990 there had only been 13 diagnosed and identified cases worldwide.A cluster of 20 cases has since been documented in the twin towns of Colorado City, Arizona and Hildale, Utah, both of which were formerly known as "Short Creek" (or the Short Creek Community). The two towns combine to form a community of 10,000 members of the Fundamentalist Church of Jesus Christ of Latter Day Saints who have a history of practicing successive endogamy, or marriage within their own communities. Nicknamed "Polygamists Downs", the syndrome has been blamed on cousin marriage, but in a larger sense is related to the reproductive isolation of a community among whom 85% are blood relatives of John Y. Barlow or Joseph Smith Jessop.Since the initial cluster from FLDS communities were reported, it is now estimated that there are 100 documented cases worldwide. See also
Hereditary leiomyomatosis and renal cell cancer
Founder effect

References
Further reading
Pithukpakorn, Manop; Toro, Jorge R. (November 2, 2010) [July 31, 2006]. "Hereditary Leiomyomatosis and Renal Cell Cancer". GeneReviews. Seattle WA: University of Washington. PMID 20301430. == External links ==