When should aspirin not be administered?

Aspirin should not be administered to individuals who are under the age of 16 or who have a known allergy to aspirin. In children and teenagers, there is a risk of Reye's syndrome, a serious condition that can cause liver and brain damage, especially when they are recovering from viral infections. This makes it highly important to avoid aspirin in that age group. Additionally, a known allergy can lead to severe allergic reactions, making it crucial to refrain from administering aspirin to individuals with such allergies.

In contrast, the other scenarios presented involve situations where aspirin could potentially be beneficial or are not contraindicated. While aspirin may not be advisable for individuals experiencing an active stroke due to the urgency of intervention required, administrating it does not carry the same risks as it does for children or those with allergies. For cases of minor headaches, aspirin is commonly used for relief, and chest pain is often associated with cardiac issues where aspirin is typically indicated as a preliminary treatment if there is concern for conditions like heart attack.