The basic reason of pimples to appear and reappear on the skin is acne. To have a good understanding of the said statement, you need to know the causes of acne.
Acne occurs due to the presence of the painful bumps that lie under the skin. It is caused due to the inflammation of the hair vesicles and sebaceous glands as a result of excessive production of sebum, hormones and the responsiveness of immune to the foreign bodies.
It is still not known that why the hair vesicles get squeezed but it is very clear that acne is the effect of obstruction of the hair vesicles. When more sebum is produced and it does not get any place for secretion, it busts the hair vesicles and blocks them with the dead skin cells. Then, as the sebum itself is not able to pop out of the skin, a lesion or a bump appears on the outer skin layer that is the whitehead. On the other hand, if the sebum pops out of the skin, then a lesion or bump so appeared is the blackhead.
Try to limit the intake of too spicy foods as it is one of the causes of acne formation. Other causes include the hormonal disturbances, poor immune system and the hereditary reasons.