Allergies can range from being annoying to downright life-threatening. A recent report suggests that as much as 30 percent of the adult population and 40 percent of children worldwide experience some type of allergy, but this number is increasing. Thankfully, not everyone is equally susceptible to developing allergies, and although some risk factors, such as a having a family history of allergies, may be obvious to most, others are far more obscure.

Our bodies’ immune systems do an awesome job of protecting us from disease by targeting and destroying foreign entities, such as viruses or bacteria. However, every now and then, the immune system can mistake an otherwise harmless substance as dangerous. When this occurs, it is called an allergy, according to Allergy symptoms, which range from the annoying runny nose to life-threatening breathing difficulties, are signs the body is trying to defend itself against what it perceives as a threat.

As mentioned, the prevalence of allergies is on the rise, especially in the United States, and one study suggested that merely being born in America could be enough to up one's chances of developing some type of allergy.

The study, which was published in the Journal of the American Medical Association in 2013, was based on nearly 80,000 children from around the world, but concluded that about 35 percent of U.S.-born children had some type of allergy disorder compared to only 20 percent of foreign- born children.

The results may back the "hygiene hypothesis" which states that exposure to dirt and pathogens at a young age is critical for building a healthy, balanced immune system. Unfortunately, some believe that America’s recent shift toward being overly clean, through the use of antibacterial soaps and gels, has deprived new generations of children of this critical exposure.

“The U.S. and other first world cultures are too clean and we are very industrialized with pollution,” Dr. Purvi Parikh, an allergist/immunologist of Allergy & Asthma Network, told Medical Daily. “Kids aren’t exposed to playing outside with dirt and we don’t have as much exposure anymore to these good bacteria that make your immune system stronger.”

Of course, where you are born is not the only surprising factor that can help increase your asthma risk. When you are born may also play a role. Although our genes are set in stone, certain external factors, such as what we eat or whether we smoke, can affect which genes are switched on and off. These are called epigenetic changes and can in turn affect one’s health. A study released earlier this year suggested that the season you were born in can cause epigenetic changes that affect your allergy risk. The research finds those born in the fall and during winter are at increased risk.

Even habits that seem harmless (and healthy), such as brushing your teeth, can up your risk. One 2012 study from Norway found that exposures to triclosan, a chemical commonly used in toothpaste as well as other cosmetic products such as deodorant, could increase likelihood of developing allergies. For the study, research tested the urine of 623 10 years olds for levels of Immunoglobin E (IgE), antibodies produced by the body in response to an allergy. Results showed that children exposed to greater amounts of triclosan had higher levels of IgE in their system and increased rates of hay fever. The researchers suggested that the reason for this was due to triclosan’s ability to change the bacterial flora in the body, a behavior that can increase your risk of allergies.

While genetics continues to be the biggest risk factor for developing allergies, Parikh recommends steps that parents can take to try and minimize their children’s risk.

“The best thing is to not be too limited in what you expose your child to,” said Parikh. “It's safe to introduce them to things such as peanuts and we've found now that early introduction reduces your chances of developing allergies in the long run. Let your child be dirty and play. There is an instinct to keep your child very clean but that may hurt them in the long run.”

Source: Silverberg JL, Simpson EL, Durkin HG, Joks R. Prevalence of Allergic Disease in Foreign-Born American Children. JAMA Pediatrics. 2013

Bertelsen RJ, Longnecker MP, Lovik M, et al.Triclosan exposure and allergic sensitization in Norwegian children. Allergy . 2016

Lockett GA, Holloway JW, and Soto-Ramirez N, et al. Association of Season of Birth with DNA Methylation and Allergic Disease. Allergy. 2016.