I sleep on my back and have acne there. What can I do to keep the acne from getting worse and prevent future acne from developing? (I'm not sure if sleeping position matters.)
While I cannot comment on the issue of laying on your back causing acne, I hope my answer helps with your concern for prevention.
There is some evidence that glycemic index (GI) is related to more severe acne. One study examining the diets of 287 people from ages 18-25 with no, mild or severe acne, found that those with worse acne had greater dietary (glycemic index). The foods which were significantly different among groups included servings of:
- Milk (with non-fat milk having more of an effect than whole milk)
- Saturated fat
- Trans Fat
- Fish (indicating higher fish consumption in those with no or less severe acne)
- Fruit and fruit juice equivalents (presumably because fruit juice has added sugar making them high GI foods)
The authors propose that GI is related to acne development because of the effect on Insulin-Like Growth Factor-1 or (IGF-1), but also highlight conflicting evidence. I will avoid further biological discussion of how this is thought to happen in the body because that is not your question.
The authors do propose that milk may be related to worse acne because it contains IGF-1 and its insulinemic response is much higher than would be expected because of its glycemic load alone so they hypothesize that the IGF-1 leads to (with a few steps omitted) greater sebaceous lipogenesis and sebum output, leading to acne.
The authors also comment on the negative relationship between fish consumption and hypothesize that n-3 polyunsaturated fatty acids (omega-3 fatty acids) have a protective effect against acne.
Study limitations include that the data are self-reported as was the acne severity.
A recent review of the dietary and acne literature indicated that there haven't been any randomized controlled trials that can conclude causally that high glycemic load, dairy and n-3 polyunsaturated fatty acids have an effect on acne. The evidence is more convincing for glycemic load, and less robust or conclusive for milk and n-3 polyunsaturated fatty acids.
The aforementioned data are inconclusive but worth taking note to see if reduction of these foods benefit your acne. See this for a in-depth discussion of the above issues.
Burris, J., Rietkerk, W., & Woolf, K. (2013). Acne: the role of medical nutrition therapy. Journal of the Academy of Nutrition and Dietetics, 113(3), 416–430.
Burris, J., Rietkerk, W., & Woolf, K. (2014). Relationships of self-reported dietary factors and perceived acne severity in a cohort of New York young adults. Journal of the Academy of Nutrition and Dietetics, 114(3), 384–392.
Pimples on the back can be either acne or staphylococcal folliculitis, that is a bacterial infection of the hair follicles, which can look very similar to acne - some pictures here. Staph folliculitis would heal on its own in few weeks or quicker with an antibiotic ointment, while acne are usually more persistent.
Pressure upon the back skin might trigger back acne, but pressure on the cheeks when lying face down could then trigger facial acne. So...
One proposed mechanism of acne development is increased activity of the androgen hormones in the skin (this does not necessary mean increased blood levels of the androgen hormones), triggered by:
- Psychological/emotional stress (PubMed)
- High intake of "quick carbohydrates" that is sugar and starch from sweets, fruit juices, soda, white bread and white rice, which results in frequent and high raises of blood glucose levels (glycemic load) (PubMed Central, PubMed)
- Dairy products (milk, ice cream, cheese), supposedly due to presence of bovine androgen hormones in milk (PubMed, PubMed Central)
A comprehensive review of acne causes and treatment (EhealthStar)