A delayed allergic reaction might occur an hour or more after you’ve been exposed to an allergen. You might also experience a biphasic reaction, in which a second reaction occurs long after the ...

Eating particular foods before exercising may bring on an allergic reaction. Peanuts, shellfish, tomatoes, corn, and wheat are associated with exercise-induced anaphylaxis, although any food can ...

Eczema, or atopic dermatitis, commonly causes severe skin itching. Learn why eczema causes a person to itch and how they can help relieve and prevent the itching.

Enzymes catalyze nearly all of the chemical reactions that occur in biological systems. Enzymes are generally proteins but also include catalytic DNA and catalytic RNA. As effective biological ...

Biosynthesis is the generation of natural products through enzymatic reactions, as in cellular metabolism. Successive enzymatic reactions by a number of enzymes are generally required to achieve a ...