Monday, 2 February 2015

Allergies on the rise

This post is another a follow up to a topic covered on the radio show I help to present - Fuse FM's Faculty of Life Sciences Society Show. If you would like to listen to a podcast of the show, click here.

It's estimated that up to 50% of children in the UK today have been diagnosed with an allergy, and the British Allergy Foundation says the number of sufferers (adult or child) is increasing by 5% every year. Clearly allergic reactions are on the increase, and doctors seem to be in a race against time to work out the cause of this incidence. In order to do this, work is being carried out all over the developed world to try treat allergies. Today I'm posting about what we as a society may be doing that is actually acting against us, and making the developed world more allergic. First, let's explore what an allergy actually is and how they work.

An allergic reaction is an adverse reaction produced by the body's immune system when it encounters a normally harmless substance. Contact with a tiny amount of said allergic substance results in bad reaction. Contrastingly, an intolerance to a substance refers to an adverse reaction produced by a substance (such as lactose) that does not involve the immune system. Can also contact/consume small amounts of intolerant substance with relatively few issues.


Source: stamfordallergy.com
Hay fever is one of the most common types of allergy.

Common allergens (substances that cause allergic reactions) include grass and tree pollen. dust mites, animal hair and a variety of foods. Interestingly the allergic reaction is common to whatever the allergen may be. Symptoms include sneezing, wheezing, itchy eyes, skin rashes and swelling.

So how does an allergy work? In a healthy person, our immune system acts to fight off invasion and infection through a variety of mechanisms and responses. One way is via use of antibodies. Normally, when the body recognises a substance in the body as harmful, antibodies attach to the substance of the harmful object and act as signals for other cells in the immune system. In the case of an allergic reaction, the body recognises the allergen and produces a specific antibody called Immunoglobin E (IgE) for it. IgE binds to the allergen. Eventually when there are enough IgEs bound, IgE will activate a different type of cell within the immune system called a mast cell. A mast cell will then trigger the release of substances from other specific cells that cause the inflammations common to allergic reactions (such as difficulty breathing, watering eyes and swelling). One of these substances is histamine. Histamine release is an inflammatory response of the immune system in an attempt to protect you from a harmful substance. However, in the case of an allergy the allergen tricks your body into thinking it is harmful.

One hypothesis is the "Hygiene Hypothesis". This is the idea that in order for our immune systems to function and develop correctly, we need to come into contact with lots of bacteria and microorganisms. This is especially important whilst our immune systems are in their early stages of development; i.e. we are children. Currently in our society there is a huge emphasis on super-hygienic food prep and cleaning products you can buy typically contain anti-microbial agents.. so, it may be that modern life is ‘too clean’. Studies have compared typical life nowadays in a developed country such as our own to how it would have been many years ago, when agriculture was much more important. Back then, families would have lived on farms, and were in regular close contact with livestock. It has been proven that children around this time presented with far fewer allergies than those today. Marc McMorris, a paediatric allergist from the University of Michigan Health System says “We’ve developed a cleanlier lifestyle, and our bodies no longer need to fight germs as much as they did in the past. As a result, the immune system has shifted away from fighting infection to developing more allergic tendencies”. Not only this, but medical advancements may have contributed to a rise in allergy incidence. In the previous 100 years there has been a huge leap in the availability of vaccines and antibiotics in the developed world. Although this advancement is largely successful and has contributed to falling death rates as well as many other positive factors, there are negatives. It seems that the more help we receive in order to prevent a disease, the less our body tries for itself and the more it relies on medicine’s support. Our dependence on antibiotics and vaccines increases as they become more readily available, as the pressure on our immune systems to develop is decreasing.


Source: cartoonstock.com
The future?

Another proposed cause for the rise in allergies is genetics. The family you are born into affects your likelihood of becoming allergic to something. For example, in the UK if you have one parent who has an allergy, your child’s risk of developing an allergy doubles from 1 to 2 in 5. Interestingly, a study by the Southampton University Hospital Foundation Trust found that there seemed to be a gender-genetic link in allergies. Of 1456 patients assessed, it was found that mothers who had eczema, which is an allergic skin disease, were 50% more likely to have a daughter with eczema. Also, a son was twice as likely to be born with eczema if his father also had the skin allergy. Although the predisposition for an allergy seems to be genetically linked, it’s important to realise that the predisposition is not for the exact same allergy. For example, both parents could be allergic to peanuts, and their child will be born with a higher risk of developing an allergy... but they could be allergic to anything (i.e. shellfish, hay fever etc.)

Some suggest that more allergies are presenting due to the food we eat - a1nd can be narrowed down to our Western diet or food avoidance strategies. Expectant mothers and new parents are often warned to avoid certain foods for a variety of reasons. Of course, most of these foods should be dodged, but avoidance of some can result in children that are more likely to develop an allergy. For example, a research team from the Mount Sinai School of Medicine found that if an expectant mother mouse was exposed to and consumed peanuts regularly the incidence of peanut allergy in baby/young mice was decreased. This was because the mother mouse passed on her protection against peanut allergies to her offspring via maternal breast milk. 
The globally-wide recognised symbol for an allergy

Another factor that may contribute to a rise in allergies could be attributed to the rise in expectant mothers opting for caesarean sections. Researchers at the Henry Ford Hospital in the US have shown that babies born via C-Section are 5 times more likely to develop allergies than those born naturally. It is believed this is the case due to a baby’s exposure to bacteria in the birth canal. Dr Christine Johnson (chair of the Henry Ford Department of Health Sciences) says, “In the gastrointestinal tract of babies born by C-section, there is a pattern of ‘at risk’ microorganisms that may cause them to be more vulnerable to developing the antibody Immunoglobulin E, or IgE, when in contact with allergens.

No one knows for definite what the root cause of increases in allergy incidence is. However, there are multiple hypotheses and widely believed analogies around this topic that pose potential solutions. Currently, the best and most accurate way of avoiding an allergic reaction is abstinence from the offending substance. However, the subject of allergies is topical and is likely to become more prominent as time goes on and more allergies are diagnosed; hopefully this increase will bring advantages such as increased funding and research to help those with allergies. 

2 comments:

  1. Very informative post! I'm very lucky not to suffer from any known allergies.

    Sarah | Sequin This

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  2. An interesting read! I never had allergies as a youngster however the past couple of years I've started to develop them as an adult in Summer!

    xo

    ReplyDelete