What are allergies?
That is an excellent question, and it's one you should ask. There are a couple of different ways we can define what an allergy is. An allergy occurs when a person with a heightened sensitivity encounters a substance that is ordinarily harmless (allergens), but their immune system interprets it as dangerous, and then overreacts.
In most cases the reaction is mild with itchiness, runny or stuffy nose, sneezing, or even a post-nasal drip. In rare, but severe cases it can be life-threatening.
Why does it happen?
It’s not entirely clear why some people develop sensitivities to otherwise harmless substances. In the case of ragweed pollen, for example, reactive or not, we're each exposed to only minute amounts each year (<1 microgram annually).
In some people this seems to be sufficient to evoke an immune response in mast cells (degranulation) and basophils. The immune response releases histamine which can cause bronchospasm and edema (swelling) which can make it difficult to breathe, causes inflammation, and mucous secretions in the eyes, nose, mouth, throat and lungs.
To help us understand why it happens, we look at cases where it doesn't happen. That takes us to the developed countries that generally have fewer allergies. Why?
Developed countries, such as the U.S.A. and Germany, have an abundant supply of disinfectants and hand-sanitizers. Many of us are obsessed with crazy levels of sanitation. The Hygiene hypothesis suggests that reduced exposure to daily challenges to the immune system results in an underdeveloped, immature defense system. Less developed countries certainly don't have our obsession with cleanliness.
Typically, the smaller rural or suburban family is more prone to allergies than a large urban family that shares exposures to many different people and things. Those growing up in busy urban environments with crowded schools and packed subways seldom develop allergies. Less stringent sanitation actually makes us stronger.
It is now acknowledged that since we have rather broadly reduced microbial exposure in society, our incidents of chronic inflammatory diseases, in addition to ordinary asthma and hay fever, have increased. Diseases such as diabetes type-1, multiple sclerosis, some forms of depression, and cancer have been associated because of cytokines (responsible for communicating between cells) that are implicated in lackluster immune disease response.
Peanuts—worst case scenario
One of the most severe food allergies that exists (still only 0.6% of the U.S. population), comes from that humble legume (no, it's not a nut). Theories abound as to the cause. One interesting observation which arose was that babies that had probably been exposed to skin creams that contained one or more peanut oils, to treat diaper rash, were much more likely to develop a significant peanut allergy.
Children that experience skin-crusting and skin-oozing diseases are up to seven times more likely to acquire a peanut allergy. The theory states that the mast cells just below the skin are exposed to the allergen via this highly abnormal route and develop a severe reaction to it.
On the other hand…
When introduced orally, even in those with a trace allergy to peanuts, the epithelial cells of the digestive tract recognized it as food with nutritional value, rather than as an allergen, and quelled the immune response. The body learned to accept it.
In the United States, Australia, and Britain there was a longstanding consensus among pediatricians that children should not be given peanut products. Pregnant and breastfeeding women were steered away from peanuts. But in a study comparing children from different nations it was discovered that the earlier the age when a child is introduced to peanuts, the less likely they were to develop an allergy.
Some brands of cookies for babies in India contain peanut products and the allergy is almost unknown there. In a 2014 study[i] peanut consumption by pregnant women was associated with a decreased incidence of peanut allergies in their offspring. Obviously young children should not be given whole peanuts because of the potential choking hazard, but peanut-flour containing teething biscuits could be just what the doctor ordered!
"Every child must eat its pound of dirt"—Old proverb
The "Old Friends Hypothesis" describes human evolution as one that took place in muddy, wet, and dirty conditions. It was inevitable that we would encounter all sorts of bacteria, microflora, worms, and parasites.
When something is totally unavoidable, rather than resist, our bodies incorporate these challenges. We have friendly little bacteria that live in our digestive tract that break down elements in food that we cannot break down ourselves. They get the nutrition they need to live, and the byproducts are given to us, which help us live. This is called a symbiotic relationship.
Have you ever wondered why diarrhea is a side effect during or after a course of antibiotics? Some antibiotics will kill off your normal gut flora and consequently your digestive process becomes incomplete and very inefficient. To help replenish the normal gut flora, indulge in some probiotic yogurt to replace the ones that were lost.
Patients demand antibiotics from their physicians. As a result, overuse of antibiotics has dulled their effectiveness. People that don't demand a pill for every little inconvenience generally have fewer allergies.
Man's best friend, living in the house with us, licking us, getting us dirty while roughhousing on the floor with us is one of their greatest functions. Dogs are happily exposed to the environment, with their bare feet touching actual soil and grass. They smell things, lick them, and eat stuff they find. They are like an environmental test-kit. And they bring all that to us, free-of-charge.
Cats help us through an entirely different mechanism. If they are outdoor cats then they do bring environmental challenges into the house similar to dogs. However, the main difference is that cats have some proteins in their saliva that can be quite allergenic. Because of their constant grooming it is always on their fur. Very few people are allergic to cat hair—it's that protein which bothers sensitive people. But kids who have a pet cat are never allergic to them when they grow up.
Rats, gerbils, mice, hamsters, ferrets, ants, fish… even a unicorn if you can find one… They're all good for training our bodies to work the way they evolved to operate.
Yes, of course people should probably still wash their hands after using the bathroom or before handling food. However, do not feel inclined to pull out the hand sanitizer at every possible moment. There is certainly nothing wrong with being clean—just don't go overboard with it.
All those things aside, make it a point to challenge your immune system. Make an effort to get out of your sanitary cave. Start a garden; take a hike; go skiing; buy a pet. Participate in the environment somehow, whether it's by cross-country train trip, or spending a couple of hours in a busy mall with different humans.
If you have a garden, let the kids eat beans or peas right off the vine in your back garden. Unless you're using some sort of chemical pesticide , they probably don't even need to be washed. Planting herbs like parsley, pepper, and mint keeps a lot of things at bay. It's all good if you can just ease off the sanitizing gel and get to know the world we live in. Don't let your immune system get bored.
(Frazier A, et.al.) "Prospective Study of Peripregnancy Consumption of Peanuts or Tree Nuts by Mothers and the Risk of Peanut or Tree Nut Allergy in Their Offspring"