Could be what I have. Cant remember the name, but it is where the skin cells do not shed properly so the oil in the skin gets trapped. All I can do is use exfoliants, especially strong AHA's to keep it at bay. Antibiotics also seem to help. Apparently it is genetic, common amongst those of Celtic descent.

Edited to add this, I remember my mother mentioning that I had the pimples when I was a baby. This info is from the Neostrata site

Keratosis Pilaris

Keratosis Pilaris (KP) is a skin (follicular) condition that appears as rough bumps around hair follicles (goose-bump like appearance) on the skin of the back and outer side of the upper arms and thighs. KP is typically most developed and noticeable in adolescent females. KP is an extremely common condition that can be cosmetically troubling but is generally not harmful in a medical sense. The condition is benign, self-limiting, and disappears with increasing age.

The bumps result from the improper shedding of scales from the skin in and around the affected hair follicles. Keratosis pilaris tends to be more severe during the winter months or other times of low humidity. It occurs because as the skin renews itself, old skin cells in the affected hair follicles get stuck, forming a scaly plug because the old skin cells are excessively adherent and do not shed easily. Each bump is a horny plug, sometimes red but only rarely itchy. The scale buildup often entraps the hair within the follicle.

Treatment of KP using moisturizing and exfoliating creams and lotions with high strength AHA or urea products may be helpful. They generally need to be applied at least twice daily and work by softening and reducing cell cohesion of the adherent skin scales around the follicle enabling them to be shed more easily. Often the use of a Buff-Puff to apply the cleansers and creams and to exfoliate the skin increases the benefits of these products. Since KP is genetic, the skin returns to its pretreatment character if treatment is discontinued. Therefore people who are prone to this condition usually benefit from the regular use of these exfoliating moisturizing products as part of their skincare regimen.

If you think you may have keratosis pilaris and are troubled by its appearance, you can seek the advice of your dermatologist or other physician.