Allergies of every kind, from mold to milk to metal, are becoming increasingly common in the United States. With a sympathetic nod to those of you bracing yourselves against this spring's burgeoning pollen count, here are 10 allergy facts that don't come up as regularly or reliably as seasonal symptoms do.
1. Allergies can give you a shiner. When hay fever strikes, pressure from nasal congestion can be so great that it causes blood vessels in the face to become constricted. The blood can't flow freely and may pool under the eyes. Blood draining back toward the heart, or venous blood, appears blue in color (compared to arterial blood flowing from the heart, which is red) and, when trapped, results in the appearance of an allergic shiner, sometimes known as "black-eye syndrome."
2. Any organ in the body can be affected by allergies. Sufferers of hay fever (allergic rhinitis) will attest that allergies can cause a runny nose, irritated eyes, and an itchy throat. Some allergic reactions can cause the skin to break out in hives or the intestines to cramp, and allergy-induced asthma takes a toll on the lungs.
"These are the common 'end organs' for allergic disease," explains Asriani M. Chiu, M.D., associate professor of allergy and immunology at the Medical College of Wisconsin. "In a severe allergic response, there can be a systemic reaction that affects multiple body systems. A bee sting, for example, can affect the cardiovascular system and send the body into shock." Consequently, any organ could potentially shut down as a result of reduced blood flow. An anaphylactic response affecting the respiratory system is similarly threatening.
In very rare cases, Dr. Chiu notes, an allergy cell called the eosinophil can target and cause isolated damage to an organ like the esophagus or heart. However, when organs such as the liver or kidneys are affected by an allergy, it's far more likely to be the indirect result of a system-wide reaction.
3. It's not pet hair that gets your dander up. Contrary to popular belief, pet hair is not an allergen—though it's still no fun to clean the sheddings of cats and dogs from your wool coat. Rather, it's the particles of pet dander (dead skin), saliva, and urine trapped in the hair, or airborne in your breathing environment, that prompt allergic reaction.
4. "Allergy-addiction syndrome" lacks credibility. Like a drug addict who craves a chemical that's bad for the body, some people claim to have an addiction to foods to which they are allergic. But paradoxical cravings are most likely explained by a typical psychological trick we play on ourselves: We always want something a little more when we know we can't have it. As Dr. Chiu notes, a child with a food allergy will instinctively spit out food that causes her mouth to itch or her lips to swell. Electing to override that natural survival instinct may be a mild form of masochism, but it's not an addiction.
5. The sharp rise in peanut allergies is still not well understood. The rate of peanut allergies in the U.S. has doubled over the past 10 years, currently affecting between 1 and 2 percent of the population. Prevalence in the U.S. may be explained by our method of processing; dry-roasting is not as popular a method in countries where the allergy is less common. Another prevailing theory is the hygiene hypothesis: Now that we're living in an increasingly sterile environment where diseases are eradicated and bacteria vanquished, the immune system may be seizing on harmless foreign antigens—essentially, protecting our system against a false threat.
A new study reverses recent health strategies. Rather than delaying an introduction to peanuts, the research suggests we might increase tolerance by introducing peanuts earlier and more
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