When cold air causes allergies (or is it a cold?)

Is that sneezing and runny nose an allergy or a cold? — TNS

I have been travelling for a month, so I have not been home in a while. When I finally came home and switched on the aircon in my bedroom, I started sneezing badly. I ended up with a congested nose and was not able to breathe properly all night. What could be the cause of this?

You probably had an allergy to something your aircon spewed out, or something in your bedroom, like dust mites.

Or this could be a case of you reacting to the sudden cold air.

Allergies can manifest because your immune system reacts to a foreign substance, e.g. dust mites, pollen, bee venom, pet hair or a certain type of food.

These things do not cause a reaction in most people, but because you happen to be susceptible to it, it causes a reaction in you.

Why is my immune system reacting in this manner?

Your immune system produces antibodies to fight what it perceives as external threats to your body.

When you have allergies, your immune system makes antibodies that identify a particular allergen as harmful to your body, even though it isn’t harmful in that sense. (It certainly is not harmful to other people).

Therefore, when you come into contact with that particular allergen, your immune system reacts by inflaming your sinuses, airways, skin or digestive system.

In your case, it reacts by inflaming your sinuses and airways.

How severe the reaction is varies from person to person.

It can range from being very minor all the way to being as severe as anaphylaxis, which is life-threatening and can cause death.

I sleep in an air-conditioned room because my husband needs the cool temperature. But the cold air seems to be making my nose congested. Is this an allergy?

This is called cold-induced rhinitis. In temperate countries, many people get it when they go outside during cold weather.

Our nose is the first entryway of our upper respiratory tract.

Its task is to warm, filter and clean the air in order to prepare it to enter our more sensitive lungs.

Regardless of the air moisture outside your nose, the relative humidity at the back of your nose is around 100%.

Your nose also keeps the average temperature back there around 25.6°C to 30°C.

When cold air enters your nose, it stimulates the nerves within your nasal cavity to activate a cholinergic pathway (i.e. one that uses the neurotransmitter acetylcholine).

This causes the blood vessels in your nasal cavity to expand and become engorged with blood, leading to nasal congestion and a lot of mucus secretion, which produces a runny nose.

This is a compensatory mechanism that is trying to maintain the optimum temperature and humidity inside your nose.

Note that by adding humidity (mucus) and warmth (congestion), your nose is trying to perform its function of filtering and warming the air.

Oh, I didn’t know that. Why me and not my husband though? He seems to be sleeping very well even with the aircon temperature at 16°C.

Some people are predisposed to being more sensitive to this reflex and may have stronger reactions.

It is pretty much like allergies; you probably have reactions to some allergens that your husband and other people don’t.

What can I do?

You can sleep in warmer aircon temperatures, such as 24°C and above.

You can also block the cholinergic pathway by taking an anti-cholinergic medication, such as ipratropium bromide.

It will decrease your mucus secretion, thus drying up your runny nose.

How can I differentiate between an allergy and a cold caused by a virus?

It is probably an allergic rhinitis if:

• Your mucus is clear or watery.

  In colds, the mucus can become thick or coloured.

• Your eyes are also itchy or watery.

  It is uncommon to have itchy eyes when you have a cold.

• Your symptoms stay more or less the same.

  Allergies may feel extra bad for the first day or two, but after that, it’s you’ll experience the same symptoms day after day.

• You’ve been sniffing for more than a week.

  A cold usually clears up in seven to 10 days, but allergies can last several weeks or longer.

• Your symptoms show up only in certain situations, such as when you are spring cleaning or when you sleep in an air-conditioned room with a cat, or are sleeping in a new hotel room.

What can I do?

Prevention is better than cure, so you can take steps to allergy-proof your home as much as possible.

Meanwhile, there are plenty of antihistamines you can take to ease your runny nose or eyes.

You can even take some nasal sprays, which can be either antihistamines or decongestants.

For people with more serious allergies and symptoms, the doctor may prescribe a steroid.

See Tell Me About next fortnight for how to allergy-proof your home.

Dr YLM graduated as a medical doctor, and has been writing for many years on various subjects such as medicine, health, computers and entertainment. For further information, email [e-mail]. The information provided is for educational and communication purposes only, and it should not be construed as personal medical advice. Neither The Star nor the author gives any warranty on accuracy, completeness, functionality, usefulness or other assurances as to such information. The Star and the author disclaim all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.