Food Allergy vs. Food Intolerance

Updated on 4th November 2008:
Last month was an allergy awareness month, so this is my belated contribution to it:
Through the blogsphere I am getting to know that the concept of allergy is not clear to all. I know, even here, people misinterpret and use the terms too loosely. But, I feel as smart blogging mothers, I expect you to know and understand it thoroughly! -
The basic difference between an Food allergy and a Food intolerance.
Allergy is an immune-reaction of the body against the foreign bodies it encounters - also termed as Allergen(s). An allergic reaction happens when the white blood cells (lymphocytes) get activated and recognise certain "harmless" foreign "protein-aceous" substances as a danger and start producing antibodies against them. These allergens could be present anywhere - dust (mites, spores), pollens, foods - fruits and vegetables, nuts, but also eggs and milk and its products. Viewed at the molecular level it is almost invariably a protein or a peptide ( a small sized protein). Now you might have heard of people having an allergy against uncooked or unroasted foods like nuts or fruits like apples, but, can eat the cooked / roasted forms, as the allergens - proteins degrade through it. But, it is usually in cases of a milder forms of the allergy. As over-activated lymphocytes is not good for ones health and can also get very dangerous.
For those showing a strong hypersensitivity to certain allergens, they need to avoid it completely, as it can be fatal for them! (Anaphylaxis) They need an immediate treatment, if they come in contact with the allergen.
Symptoms of an allergic reaction are listed here.
The best thing to do when one notices the first signs of allergic reactions to certain things is to talk to ones doctors and take care of the allergy at an early stage. As, one can get oneself desensitised to many of the allergens and prevent them from getting worse.

Food Intolerance: This is usually the body's response - a much slower one as compared to an allergy - caused by its inability to produce certain enzymes or other digestive substances, otherwise present in a healthy body. The reasons can be varied, genetic, but also environmental. Some common examples of intolerance are:
Lactose intolerance and
Gluten intolerance (also called coeliac disease; Not gluten allergy!).

The less common ones for example: Fructose and sucrose intolerance, or intolerance towards certain medical drugs or also salicyclate intolerance (Active principle in Aspirin).


An allergic reaction involves a hypersensitive reaction through antibodies and the white blood cells, whereas an intolerance does not - it is more a metabolic defect.

Hope I didn't make things even more complicated than they already were! If, yes, write your comments here or contact me.

Update on 4th November:
Tharini has also put a similar but very good information of clarification on both (here).

Many of you have actually made me check on one point about lactose intolerance once again. I keep hearing from many that they were or their child was temporarily intolerant. It confuses me, as it is the enzyme lactase we are talking about which breaks down lactose (a disaccharide) into glucose and galactose, which can then be absorbed by the intestine into the blood. I checked in wikipedia and am going to ask Rishab's doctor too. Normally the situation is like this:
1) either the enzyme is there in abundance or
2) its production is reduced or
3) it is almost absent. It has genetic and environmental factors.
But (I had not gone into details about this part of the information), sometimes it can get temporarily interrupted (source: wiki) :

• through infections of the gastro-intestinal tract like gastroentiritis.
  
• But, this is, as I understand, a very short term interruption, i.e., lactase production would restore as soon as the disease is over or the intestinal wall is healthy which would normally be within weeks.
  
• Another reason is the lactose overload, i.e., not enough lactase can be produced to break down the lactose sugar. Another very intersting point which was unknown to me (I'm not sure about its correctness)

I just found a very good link on Lactose Intolerance at kids health.org, which points out more situations where it can arise temporarily.

IMPORTANT NOTE: I'm not a doctor and any information given here does not replace the guidance required by a doctor in both the forms of medical conditions mentioned above!

Here are some more informative posts from fellow bloggers about their personal experiences and on Food Allergies:

• Tharini's Post on the same topic
• On Food allergies at Karmickids
  
• Childhood allergies at Sujatha's Blogpourri
• Dotthoughts at Karma Calling
• Monika's at Everyday life
• Sundar Narayanan's personal story
• Indianmommies