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As a graduate student rotating through medical clinics, I once heard a patient say, “Good morning, I think I am allergic to water.”

At the time, the idea of a water allergy seemed absurd to me. But as the human body constantly tries to adapt to a rapidly changing world, unusual allergies are cropping up everywhere.

Up to 50 million Americans, including millions of kids, have some type of allergy. Allergies occur when your immune system overreacts to a foreign substance called an allergen. Allergens cause symptoms that range from sneezing and watery eyes to body rashes and, in severe cases, a life-threatening reaction called anaphylaxis. The best way to control allergies is to avoid or remove the allergen and to treat symptoms.

While it’s not really possible to be allergic to your job—sorry about that!—it may not be your imagination if you think you are allergic to your shower. The most common allergens are food, drugs, pollen, dust and mold, but you can also develop unusual allergies to all kinds of common things, including:

• Water: Up to 60 percent of the human adult body is water, so it is surprising that you can be allergic to it. Aquagenic urticaria is an incredibly rare—and untreatable—syndrome where the skin erupts in rashes whenever it comes in contact with water. Tears can even trigger symptoms in some people. In severe cases, people with this disorder can have trouble breathing after drinking water.
• Exercise: Some people are truly allergic to exercise, experiencing severe itching approximately 30 minutes after working out. One type of exercise allergy called cholinergic urticaria seems to be triggered by sweat. Others such as exercise-induced angioedema cause symptoms no matter how intense the physical activity is.
• Sun: Overexposure to the sun can cause sunburn and other damage in most people. But people with photodermatitis have skin so sensitive that even the mildest exposure causes skin rashes. Those with this disorder must spend most of their lives in darkened areas, going out only at night.
• Cold: Fifteen to 25 percent of Americans are allergic to the cold (cold urticaria). People who have intense physical reactions to low temperatures may experience skin rashes and hives, swelling, fatigue, anxiety and headaches. Wheezing or trouble breathing may also occur, but these potentially dangerous symptoms are very rare.

Scientists are working hard to eradicate the symptoms and to improve quality of life for people with allergies both common and rare. In Dr. Patricia Silveyra’s lab, we investigate the effect of allergens and environmental pollutants on lung inflammation to develop therapeutic treatments for respiratory diseases.

Nathalie Fuentes is a PhD candidate in the biomedical sciences program at Penn State College of Medicine. Her studies in Dr. Patricia Silveyra’s lab include the development of sex-specific therapies to treat lung diseases, sex differences in asthma-related lung inflammation triggered by ground-level ozone and the role of male and female sex hormones in lung disease. Nathalie is originally from Caguas, Puerto Rico.