Allergic reactions are a part of your body's natural defense mechanism. When confronted with a substance which your body considers toxic, your body will try to get rid of it, attack it, or somehow neutralize it.
If it is something that lands in your nose, you might get a runny, sneezy nose. If it lands on your skin, you might get blistery skin. If you inhale it, you'll get wheezy lungs.
If you eat it, you may break out in itchy red hives all over your body. Allergy is a definite stress, requiring large changes in energy expenditure on the part of your body's defense system to fight off what the body perceives as a dangerous attack by an outside toxin.
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