Why do we have tonsils?

The palatine tonsils sit on either side of the back of the throat and are part of a ring of lymphoid tissue called Waldeyer’s ring, which also includes the adenoids. Their surface has deep pits called crypts that trap bacteria and viruses so immune cells can learn to recognise them. They are most active in childhood, when the immune system is meeting many germs for the first time, and they generally shrink after puberty. Because they are frontline tissue, they can become infected themselves, causing tonsillitis. Removing them (tonsillectomy) is common, and the rest of the immune system usually compensates well.