Like many, I deal with allergy for past several years and thought I share my findings with you. Here it comes:
The latest surveys show that the rates of allergy are increasing throughout the world, affecting up to 30-35% of people at some stage in their lives. This increase was initially seen in countries such as the UK, Europe and USA, but can now be found in all countries undergoing industrial development. The pattern of allergy is also changing – initially, the increase was in asthma and allergic rhinitis (hay fever). However, recent studies have confirmed a significant increase in the incidence of food allergies, in particular amongst children. In the UK, it is estimated that up to 50% of children are diagnosed with an allergic condition.
What is Allergy?
Allergy is caused when the body’s immune system reacts to a normally harmless substance, such as pollen, food, or house dust mite. The body identifies the substance as a threat and produces an inappropriate, exaggerated response to it. What we are only beginning to understand is what tips the balance in favor of allergy. Researchers have suggested that a number of factors might cause someone to become allergic:
Children born into families where allergies already exist have a higher than average chance of developing allergies themselves. In the UK today, children have a 1 in 5 predisposition of developing an allergy. However, the risk is doubled if one parent has an allergy (particularly if that parent is the mother). If both parents have allergies, the risk is increased to 60-80%. This increased tendency for individuals to develop allergies because of their genes is known as being Atopic.
The Hygiene Hypothesis
After many studies and much research, the resulting hygiene hypothesis suggests that early life exposure to suspected allergens actually immunizes a child from developing allergies later in life. It further explains that in developed nations, the elimination of childhood diseases and the routine of a cleaner lifestyle than in poorer nations actually interrupt the healthy development of the immune system. Thus, people from the most developed nations incur the highest incidence of allergies because their immune systems work improperly.
‘The hygiene hypothesis and its implications for hygiene‘ compiled for the International Scientific Forum on Home Hygiene (IFH)², evaluates the various medical, public health, and environmental and lifestyle changes that might have altered our exposure to microbes, and outlines the various other theories put forward to explain the rise in allergies. It has been produced by Dr. Ros Stanwell-Smith³ and Professor Sally Bloomfield4, Honorary Professor at the London School of Hygiene and Tropical Medicine’s Hygiene Centre.
The report finds that there is significant evidence that changing exposure to microbes¹ may indeed be a factor in the rise in allergies. But it finds no evidence that cleaning habits prevalent today are to blame and it firmly dispels the notion that we are living in super-clean, germ-free homes.
Changes in the foods we eat
Our diets tend to include more processed foods and less fruit and vegetables. It has been suggested that the increase in food allergy might be due to more allergenic foods, such as peanut, in our diet. However, there is no evidence that this has happened, and many cultures traditionally eat high amounts of certain allergenic foods, for example, peanuts in some Asian communities.
A number of research teams are investigating whether reduced levels of nutrients – in particular vitamin D, omega-3 fatty acids (in fish) or antioxidants – might contribute to the development of allergy. While a diet low in oily fish has been associated with increased risk of childhood asthma and allergies in some studies, one study giving extra fish oils to babies did not prevent the occurrence of allergies.
Vitamin D is important for the immune system and in early lung development. Deficiency of vitamin D is increasing throughout the world mainly because of sunlight avoidance through spending more time indoors or using sun-screen to reduce risk of skin cancer (most vitamin D is produced by the action of natural sunlight on skin). However, the data linking vitamin D deficiency to allergy is conflicting. Furthermore, giving pregnant women vitamin D supplements does not appear to have a consistent effect on reducing the risk of allergies in children.
Our environment today is very different from 50 years ago. While there is evidence that pollutants can exacerbate existing airway allergy, the question of whether pollution can cause new allergy remains controversial. One hypothesis for which there are accumulating data, is that the increase in allergy mirrors our declining exposure to bacteria and other micro-organisms in our environment. This has led to the Hygiene Hypothesis.
So an intriguing possibility is that many of the above dietary and environmental factors may increase allergy risk by regulating genes which promote an allergic-type immune system. Hopefully, our understanding of epigenetics will increase over the coming years, offering new potential strategies by which we might be able to prevent allergy.