Summertime Sadness

(Source: ijbrownopticians.co.uk)

It’s summertime. The sound of lawnmowers starting up should beckoning us outside, announcing that the sun is out. Except, that to the hay fever sufferer, the knowledge that someone somewhere is cutting grass reduces us to tears - quite literally.

So what exactly is hay fever? The scientific terms allergic rhinitis or pollinosis describe a collection of symptoms mainly affecting the nose and eyes. Hay fever, which one fifth of the population suffers from, leads to summer scenes glimpsed only through watering eyes, and leisurely picnics disrupted by an itchy throat and a running nose. Less well known effects include difficulty sleeping and concentrating.

Bizarrely, hay itself very rarely causes the allergic reaction. Instead hay fever sufferers are usually hypersensitive to grass pollen. Certain tree pollen can also be a culprit. The highest pollen levels occur in the late spring and early summer. Alternatively exposure to airborne particles of dust can also trigger the exaggerated, misplaced immune response. The reaction cascade goes something like this:

1. Initial exposure to the allergen takes place through inhalation of pollen, mould spores, or dust mites. Your body produces the antibody ‘Immunoglobulin E’ (IgE) which has been designed specifically for that particular allergen, but you won't experience a reaction yet. If you are atopic (which means you’ve inherited a predisposition toward allergic disease), your immune system cells are quick to stimulate antibodies. They bind to special receptors on your immune cells and ‘sensitizes’ your body - priming special cells called ‘mast cells’ for action.

2. Next comes the early-phase response upon re-exposure to an allergen. When you are re-exposed to an allergen, like pollen, the IgE of mast cells binds to the allergen. Mast cells explode with histamine and other inflammatory substances, called mediators, which spread through your system. That’s when it all kicks off: you start to itch, wheeze, cough, and sneeze. And all of this within just one hour of initial exposure.

3. The late-phase response to an allergen actually begins at the same time as the early-phase response but takes longer to appear. This late-phase response often involves immune cells called eosinophils. It can last for a whopping 24 hours or so before tailing off. It’s in this stage that congestion and irritability can be worse than they were during that initial response.

It’s not fully understood why some people develop hay fever, however several risk factors have been identified. If you have a close family member with hay fever, chances are you are likely to suffer from it to some extent. It’s also been shown that there is a slightly higher risk if you or your relations have any allergy at all. A significant number of asthmatics have hay fever too.

Interestingly, people born during the high pollen season have a slightly higher risk of developing hay fever than other people. Infants and babies regularly exposed to second-hand cigarette smoke are also more likely to develop hay fever than babies who aren't. This fits with the research showing that smoking worsens pollen allergies. Studies also show that a higher percentage of firstborn children eventually develop hay fever, compared to others. An asthmatic child first born to a family of hay fever sufferers, I never really stood a chance.

Scientists have looked into the prevalence of hay fever and found that children on farms are less susceptible to the disorder. In one study having farming parents was significantly associated with lower rates of sneezing attacks during the pollen season. It suggested that children growing up on a farm were less likely to be sensitized to common allergens and to suffer from allergic diseases than children living in the same villages but in non-farming families. Factors directly or indirectly related to farming as a parental occupation could be considered here. The research supports the so-called hygiene hypothesis, which predicts that the rising rates of allergies can be blamed on societies that are in fact too clean.

Now comes the question of how to treat the allergy. Everyone will have heard of antihistamines and as you can guess from the name, they get to work by counteracting the effects of histamine. Antihistamines, antagonists to the H1 histamine receptor, which histamine must bind to, to exert it’s effect, help to prevent an allergic reaction from happening whereas corticosteroids, a form of steroid treatment very effective for hay fever, instead simply reduce levels of inflammation and swelling.

Promisingly, clinical trials being run by PollenLite, aim to test a new type of vaccine for hay fever symptoms. If successful, the vaccine should actually prevent the allergy by halting the immune response. Novel aspects of this injection include the fact that it uses smaller volumes of vaccine and only shallow penetration of the skin.

#EllieWilliams #Hayfever #Biology