“What is food for one person may be poison for another.”
Lucretius, 75 B.C.
Although less than 2% of the population suffers from food allergies, it is estimated that more than 20% suffer from food intolerances.
Food allergies are immediate and obvious, like an allergy to peanuts, to shellfish, to eggs, and the reactions may be harsh. Some of the symptoms may be sneezing, swelling, rashes, skin irritation, weakness, and they can vary widely in severity. Usually in this type of allergies the immune system produces IgE antibodies to defend itself against the enemy, which in this case is food or some ingredients; this is how unwanted symptoms are created.
Food intolerance is characterized by a delayed reaction; symptoms may occur after hours or days of eating the food. For example, if our body lacks some enzymes such as lactose we experience adverse symptoms when drinking milk or consuming dairy. Other symptoms of lactose intolerance may be bloating, severe drowsiness and confusion. We also may have no physical symptoms at all and then the situation is more complicated; since symptoms may appear up to three days after eating the food, we can not be sure which food caused the intolerance.