This allergy


  • Health
  • Sunday, 16 Mar 2003

BY COLIN KHOO

HOME sweet home, they say. Where else would things familiar and old habits dwell so well? Yes, but home too is where the old allergies are preserved, amongst other things. The heavy upholstered furniture, the bed sheets, the curtains and the carpets – they all are home, not only to us, but to all those allergens (substances that trigger an allergic reaction) as well. High on this list of allergens are dust mites. 

“The home environment traps allergens well. Take dust mites for example. Almost every household is affected. And the way in which they breed and feed ensures that they thrive,” says consultant immunologist Dr M. Yadav.  

These days,mattresses are made in suchDr M.Yadav...If a person is allergic tomites and inhales the pellets,his/herbody would produce IgE antibodiesdirected against the mite allergen.'

“The life-cycle of a house dust mite is about three months. And every month they will leave about 50 eggs, which hatches within 25 days. Therefore if you have a million mites, just imagine how they would multiply. After leaving their eggs, in 25 days you would have 50 million mites,” notes Dr Yadav.  

It’s not the mites themselves, though, which triggers off an allergic reaction. “Living mites are not the problem. Rather, dead mites and faeces; and on average a mite releases 50 pellets of faeces. These pellets will stick together sometimes and they are highly allergenic,” adds Dr Yadav.  

Furthermore, it is also common to mistake these droppings for mere dust. Ever came back from a long vacation to find the bed sheets dusty and wondered how the dust got in even with the windows closed?  

As Dr Yadav says: “The usual thinking would be that dust had come from the outside, but this is not true – it comes from within the mattresses or other thick upholstery. When you inhale this, you would start sneezing as these pellets are highly allergenic.” 

And how, one might ask, do these mites feed? “They survive by eating funguses and skin scales. We drop about 1g of skin per day and a hundred thousand mites can live on that for six months. So, there’s no problem at all for them to multiply and perpetuate their existence.  

“And there’s another thing to be aware of. These mites do not live on the surface of the bed but inside the mattresses. These days, mattresses are made in such a way that they are very foamy, so it is cooling from the inside. This makes a very nice habitat for mites to multiply.  

“And these pests come out only at night as they are photophobic. They are so small, about 200 microns in size, that they can go through most of the bed sheets. On a rough estimate, a mattress would have five to 10 million mites, and if a person has even a mild allergy, they only have to breathe in one microgram of house mite dust to trigger off an allergic reaction,” says Dr Yadav.  

It is estimated that a quarter of the population in Malaysia is allergic to house mite pellets (considerably lower than in the UK, where 40% of the population is allergic to it). So why is it that some are allergic to it while others aren’t? 

Dr Yadav explains that this is simply because everybody’s immune systems react in a slightly different way to these allergens. “When you inhale these pellets, your mucosal tissues (cells inside the nose) react to it. And since these allergens contain certain enzymes as they come from the guts of the house dust mites, they penetrate the mucosa very rapidly and cause a reaction. 

“So an allergen might cause a person to start off with a mild running nose. This might, subsequently develop into a blocked nose and might persist for a long time. In the early phase reaction, only a few cells are affected by the allergen. 

“However, in most cases, 60% of people sensitised to allergens will go on to the later phase and would have what we call perennial allergy. Persistent rhinitis (inflammation of the nasal cavity) is one example,” says Dr Yadav. 

In addition, most asthma patients react adversely to house dust mites. “This is so as these pellets might start moving down and affect the bronchial area (the main passageways of the lungs). This might start an asthma attack. About 90% of asthma patients are sensitised to house dust mites.”  

One should be aware that, apart from dust mites, other particles or things that find a roosting ground in homes can also trigger an allergic reaction. “The saliva and scales of cats, for example, is highly allergenic. Cockroaches too are problematic. In Malaysia, 67% of the people with asthma react to that pest.  

“Apart from pets and pests, pollen is also allergenic. The pollens that affect our country are largely from oil palm. People with severe rhinoconjunctivitis (eye and nose allergy) are likely to react to such pollen.  

“To reduce the incidence of allergic reaction, people have to manage their homes. This could be done through certain methods of filtered vacuuming, sanitisation and dust-mite treatment,” says Yadav. 

And that’s not the end to the story of allergens, not by a long way. Unfortunately, there’s a host of other things that could trigger off that dreaded reaction. “Take food for example. Many people are allergic to certain kinds of food. However, when it comes to food, one has to recognise the difference between intolerance and allergy. In the case of intolerance, the problem is caused by the lack of certain enzymes to process the foodstuff. Normally, a person would only suffer from intolerance if he consumes a considerable amount of a food he can’t process. In the case of allergy, however, even a very slight amount might trigger off an allergic reaction,” says Dr Yadav. 

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