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Coceira vs. comichão vs. prurido

Word practice demo
While coceira, comichão, and prurido all describe the sensation of itching, the choice depends largely on regional differences (Brazil vs. Portugal), the level of formality (casual vs. medical), and specific nuances regarding the type of sensation.

Coceira

A2
This is the most common, everyday word used to describe an itch, particularly in Brazil. It applies to any general itching sensation, whether from a bug bite, dry skin, or an allergy. It is informal and widely used in daily conversation.
Eu tenho uma coceira horrível nas costas.
(I have a horrible itch on my back.)
A picada do mosquito causou muita coceira no meu braço.
(The mosquito bite caused a lot of itching on my arm.)
Se você tem coceira, tente não arranhar a pele.
(If you have an itch, try not to scratch your skin.)

Comichão

B1
In European Portuguese (Portugal), this is the standard everyday word for an itch, used similarly to coceira. However, in Brazil, comichão implies a specific tingling or tickling sensation, or is used metaphorically to describe an intense urge or restlessness to do something.
Sinto uma comichão no nariz, acho que vou espirrar.
(I feel a tickle in my nose, I think I'm going to sneeze.)
A etiqueta da camisa está a fazer-me comichão no pescoço.
(The shirt tag is making my neck itch.)
Ela sentiu uma comichão de vontade de viajar pelo mundo.
(She felt an itch (strong urge) to travel the world.)

Prurido

C1
This is the technical, clinical, and formal medical term for an itch. You will mostly hear prurido in a doctor's office, read it on medicine leaflets, or see it in advertisements for dermatological creams.
O paciente queixa-se de prurido intenso na região abdominal.
(The patient complains of intense itching in the abdominal region.)
Este creme é indicado para o alívio rápido do prurido.
(This cream is indicated for the rapid relief of itching.)
Um dos efeitos secundários deste medicamento é o prurido.
(One of the side effects of this medication is itching.)

Summary

To summarize: use coceira for casual conversation in Brazil; use comichão for casual conversation in Portugal or to describe a tingling/metaphorical urge; and use prurido only in medical or highly formal contexts.