What could cause intense itching all over the body within seconds of entering public places like libraries?

Itching all over the body within seconds of entering public places like libraries is probably _not_ caused by those locations themselves, but rather something you are carrying/wearing.

Common causes of sudden itching include:

- Allergic reactions: Certain allergies, such as those to dust mites, pollen, or even certain foods, can cause itching all over the body.

- Contact dermatitis: This is a skin irritation that occurs when your skin comes into contact with an allergen or irritant. Common triggers include poison ivy, latex, and certain metals.

- Hives: Hives are red, itchy welts that can appear anywhere on the body and are often caused by an allergic reaction.

- Scabies: This is a skin condition caused by tiny mites that burrow under the skin. Scabies causes intense itching, especially at night.

- Drug reactions: Some medications, such as antibiotics, can cause itching as a side effect.

It's important to see a doctor if you're experiencing sudden, intense itching all over your body. The itching could be a sign of a serious underlying condition, such as a thyroid issue or certain cancers.