1. Semen Aleksandar Bedov / Getty Images Human seminal plasma hypersensitivity is thankfully not very common. It can cause vaginal swelling, burning, and itching within 10 minutes after you do the nasty, according to a 2008 study. The cure? MOAR SEX! Seriously. One patient was instructed to have sex every 48 hours in a process called "intravaginal desensitization," and it was apparently a success. 2. Water Michael Blann / Getty Images How can this be when WE'RE MADE OF WATER?? According to this 2011 study, people who have aquagenic urticaria can drink water without any problems, but they get itchy hives if they're submerged in water — whether it's a pool, shower, or lake. Nobody really knows what causes the reaction, but some theories propose that it may have something to do with salt concentration or the chemicals present in water. 3. Nickel Coins Fuse / Getty Images This is actually a pretty common allergy (more women are affected than men). People who are allergic to coins containing nickel break out in an itchy rash, according to American Osteopathic College of Dermatology. The allergy is usually caused by prolonged exposure to nickel. 4. Some Flip Phones and BlackBerries Kimberrywood / Getty Images People are actually allergic to the nickel or cobalt that are found in BlackBerries and flip phones, according to a 2013 study. Droids and iPhones did not test positive for nickel or cobalt. Unfortunately, nickel allergies have increased among all age groups in the United States, but luckily the allergy has decreased among younger people in the European Union (thanks to nickel regulation). 5. Clothing Tim Pannell / Getty Images Clothing dermatitis can be caused by a bunch of things.While some people are allergic to wool or cotton itself, most clothing allergies are a result of synthetic things like rubber materials, formaldehyde finishing resins, chemical additives, dyes, glues, and tanning agents used in processing the fabric, according to the Washington State Department of Labor and Industries. 6. Sunlight Erproductions Ltd / Getty Images Photodermatosis is actually not that rare and may affect 10% to 20% of people in the United States. It causes an uncomfortable rash, but it's not life-threatening, according to a 2008 study. Usually, people begin to feel the onset of symptoms in their twenties or thirties. 7. Sweat Luca Francesco Giovanni Bertolli / Getty Images According to a 2010 study, cholinergic urticaria may actually be caused by unknown substances in sweat, which produces hives. But nobody is really sure about the true cause. 8. Wood Dust Hans Hansen / Getty Images People who are most at risk are carpenters, according to the Centers for Disease Control and Prevention. It can cause a whole bunch of nasty allergic symptoms like skin reactions, sneezing, and other respiratory ailments. 9. Cold Weather Kjekol / Getty Images A 2012 study found that people with cold urticaria developed hives after their skin was exposed to cold weather, ice cubes, or cold liquids. The participants in the study didn't develop the allergy from exposure (unlike carpenters who are allergic to wood); instead, they inherited the condition. 10. Deodorant Gpointstudio / Getty Images There are a bunch of deodorant ingredients that can cause an allergic reaction, but the most commonly used allergen found in deodorant is fragrance, according to a 2008 study. In fact, 90% of all deodorants at Walgreens contained fragrance. The second most common allergen is propylene glycol. Other allergens include parabens, essential oils, vitamin E, and lanolin, which can make your skin break out in rashes. 11. Latex Richard Semik / Getty Images This can be a problem for health care workers who frequently wear latex gloves, but other people can be exposed to latex from their underwear. In a 2006 study, 20% of nurses tested were found to have to a skin reaction when exposed to latex. Around 2% of the nurses developed respiratory symptoms. 12. Sulfites in Beer and Wine Innovatedcaptures / Getty Images Around 1% of people in the United States have a sulfite allergy, according to a 2014 study. Some people experience a flush, while others get rashes. In rare cases, the allergen may cause asthmatic symptoms or diarrhea.