Respiratory Allergies - Can it be avoided?

Our exposure to allergy is absolute. There are very few places on earth that have relatively low allergens (think the Alps and Arctic!). To develop allergy, we must be genetically predisposed and must have sufficient exposure to allergens. To date, there have been many candidate genes identified for different allergies. However, inheriting these genes alone is insufficient to trigger allergies. One needs sufficient exposure time to allergens to develop allergies.

So, can a newborn be born with allergies? It's interesting to note that amniocentesis (Amniotic fluid) studies recently have shown the presence of allergic chemokines (chemicals that mediate allergies). We are not sure how and why this happens but epidemiological studies seems to suggest a connection between allergic and smoking mothers and the birth of an allergic child (atopy).

Another interesting finding is the association between the amount or level of allergen exposure and the development of allergy. Any allergist or doctor will tell you to get rid of your pet cat if you or your family members suffer from asthma. It's interesting to note more allergic and asthmatic children are born to mothers with low or partial exposure to furry animals (like cats). In household with many cats or furry animals, the incidence of birth of an asthmatic child is lower that that of household without pets. So, experts are re-thinking on the total avoidance advice for asthma at least-maybe what they need is lots more feline friends at home!

There have been a few systematic reviews on the efficacy of allergy avoidance. One review in particular focused on all allergy avoidance studies done in the past 10 years. The conclusion-allergen avoidance does not help in reducing allergic disease.

Don't despair, all's not lost, as there are a few individual clinical trials on asthmatic and rhinitis patients that support definitive allergen avoidance measures to alleviate or improve symptoms.

By far the most common allergen to trigger respiratory allergies (allergic rhinitis , asthma, atopic cough) is the House Dust Mite (HDM). Lets be clear- it's not the dust mite one can be allergic to, rather to its droppings (poo) that are a fraction of a micron in size (a few thousandth of a millimeter). There are so minute that it takes an electron microscope to view them. HDMs live a very contended life within our mattress, pillows, duvets and indeed, in any fabric. Soft toys are another common habitat of HDM. HDM feed on our dead skin that we shed daily. A warm humid climate (as in the tropics) are a fertile ground for its propagation. Millions of HDM live and thrive in a single mattress; the HDM droppings are minute enough to pass through normal weavings of the matress and bedsheets to float freely in the air. It's not easy to dust or clean mattresses, however if you are an asthmatic with frequent symptoms, it's advisable to get anti dust mite bed and pillow covers. There are basically 2 types of these covers- acaricide (an anti-mite chemical) infused and non chemical based covers. My personal opinion is biased toward the non chemical covers as there has not been any extensive studies on the long term effects of acaricide on an asthmatic child as presumebly they would inhale these chemicals on daily basis.

There are a couple of studies on the efficacy of different vacuum cleaners on HDM population. Generally speaking , water based vacuum with HEPA filters seem to be superior in its deep vacuuming of mattresses. If you are cat allergic, its best not to allow your pet indoors as studies show they tend to sneak into your room when your back is turned. Allow me to correct another misinformation - cat allergens are found in the cat saliva and not in their fur. When a cat licks its fur as they normally do, the saliva deposited in the fur dries over time and releases very minute sized allergens in to the air. This is why a cat sensitive individual sneeze just on entering a house with cats ; even when the cats are not there. Cat allergens tend to stay for years even after the cat is gone.

Although frequent vacuuming reduces allergy symptoms, the sheer effort of daily vacuuming is only done by the most committed parent. Mopping with mild soap and water is superior to sweeping the room as this may lead to dispersion of allergens into the air. Replacing carpets with hard floor (wood or tiles) are easier to clean than frequent vacuming. While maintaining low humidity (50%) and temperatures (24C) in the room is said to decrease the HDM count, it is not always practical in the tropics. Select furniture made of leather or wood for easy cleaning and avoid soft toys on beds and cots.

And last but no least, select anti-mould paint and low VOC (Volatile Organic Compounds) to decorate the house.

Allergy Medications

Allergy medications are dispensed in many forms, namely tablets, liquids, inhalers, drops, topical creams and even as injections. Now, lets take a brief look at some of them.

1) Antihistamines (AH) - this forms the front line of an allergy. They are classified into many groups acceding to its sedating properties. They work mainly by nullifying the effects of the main allergy chemical in our body i.e. histamine. Some of the more common antihistamines prescribed by doctors are cetrizine (levocetrizine), chlorpeniramine, benadryl, and loratidine (desloratidine). Antihistamines reduces the symptoms of allergy such as itch, runny nose, sneezing and allergic rashes (not eczema). Aside tablet forms, AH is also available as eye/nose/ear drops. Intranasal antihistamine are also gaining popularity.

2) Corticosteroids (CS) - While Steroids may send shivers down the spine of some patients, we have to bear in mind that they are naturally occurring in the human body. Steroids are absolutely essential for the normal functioning of the body. While I will not go in detail on its role, suffice to say that a large part of our hormone are steroids in nature. It is interesting to note that from the diagram above, we can see that Cholesterol is the starting point in chemical pathway for the steroid formation. This is why I always tell my patients that having some cholesterol is essential for the body. Anyway, not to digress, steroids here are used to suppress our hyperactive and confused immune system form overreacting; thus causing allergic symptoms. Having said that, it is also important to note that steroid are not usually the first line treatment by the doctors except in severe cases.

3) Monteleucast (Singulare) - mast cell stabilizers that reduces the release of allergy chemicals forms mast cells. This makes this drug ideal for chronic allergies and asthmatics. It is not used in an acute allergic episode. The drawback of this drug is its cost.

4) Allergy shots - these are actually a form of immunotherapy. Once the offending allergen is known, the allergist will inject carefully titrated doses of allergens every fortnight. The rationale behind this treatment is by allowing the body to accept the allergen and not to fight it. These injections are very costly, and are not given as a routine.

5) Immunotherapy - is the cutting edge of allergy treatment. It can be said allergy treatment is leading the way in possible future treatment of all illness. For the first time, we can actually modify our immune system not to overreact to allergens. So far there are immunotherapy to treat allergies to house dust mite, bee/wasp stings and tree pollen allergens. Immunotherapy can be injected as a fortnightly injections for 2-3 years (Ouch!) to make our immune tolerate to pollen or bee sting. Currently Immunotherapy for house dust mite and tree pollens can be administered as drops below the tongue daily. This method has gained more acceptance and is proving to be a success in North America & Europe. Its use is limited in Asia due to its cost (about Rm 400-500/months x 2 years).

6) Epipen - This is a life saving device prescribed to patients with history of a serious Anaphylatic reaction. An anaphylactic reaction is the most serious form (life threatening) of allergy. Symptoms of an anaphylactic reactions include chocking, coughing, vomiting and shortness of breath on exposure of allergy. It usually occurs to food allergy such as seafood, nuts and even some fruits. Epipen is an automatic injection that is pre filled with epinephrine. The patient is thought to recognize symptoms of anaphylaxis and how to use the epipen device. In Malaysia, its availability is scarce and many doctors are not trained in its use.