What are the possible causes of pimple-like red spots around the upper body? (Photo)

Sorry to hear that you are bothered by these spots since the age of 12. Apart from all the possible causes listed by Dr Ker, the other common diagnosis is keratosis pilaris, which is a common and harmless inheritable skin condition that is caused by the build up of skin around your hair follicles. These are commonly seen on the upper arms and thighs. This skin condition is noticeable around pubertal age and will persist into adulthood. Occasionally it can be red and inflamed due to exercise or sweat. Hope this helps.

Thanks for the question. Pityriasis rosea is a condition that typically presents with scattered red rashes on the trunk and arms and thighs which may be scaly. The face is often spared in this condition. There is a herald patch, often a larger patch that appears before the rest of the rashes, but this is not seen in all cases of pityriasis rosea. The face is also a very unusual site to get the herald patch. So overall, it is really difficult to comment if your rash is truly pityriasis rosea without seeing your rashes.