I’m a 17-year-old girl who has pimples on my extreme lower back. I’ve tried several medicines but in vain. This has left me severely depressed.

The sudden eruption of “pimples” exclusively involving the area you mention most likely indicates an infection, most commonly bacterial primarily targeting the hair follicles, a condition known as eruptive folliculitis. Hair follicle infection can be caused either through direct contamination of the skin after coming in contact with another infected source, or it could be initiated by follicular injury of any nature, for example, shaving, lasering or waxing the body hair, or by vigorous scrubbing of the skin. These traumatised follicles initially developed an inflammatory reaction which later become an attractive site for bacteria to invade. Hot oil deep body massages can also cause such eruptions. The closest differential diagnosis will be acne eruptions, but this is unlikely. A much rarer differential diagnosis can be dermatitis herpetiformis – a condition producing similar skin lesions which are more vesicular in outlook and are very itchy. This is usually associated with gluten sensitivity and celiac disease of the gut. The above mentioned skin conditions/ailments are treatable. All it needs is patience and immediate treatment.

I am quite confused when it comes to choosing a suitable shampoo. Is there a guide to picking the right ones?

Shampoos are specialised cleansers designed to beautify hair and in some cases treat or prevent certain scalp diseases. They are intended to remove sebum, sweat components, dead skin cells, styling products and environmental dirt from hair. Shampoos are a complex formulation containing detergents, foaming agents, conditioners, thickeners, opacifiers, keratolytic agents, softeners, fragrances, preservatives and many other additives. Detergents are the primary sebum and dirt removal components but their excess can leave the hair dull, susceptible to ‘static electricity’ making it difficult to comb. Shampoos claiming high cleansing, antibacterial or antifungal properties have increased detergent concentration. Then there’s the issue related to the pH value of the shampoo. Anionic detergents make high pH-value shampoos and claim deeper cleansing, but usually leave the hair harsh and dry. Cationic chemical characteristics make shampoos with lower pH values. These shampoos have relatively poor detergent effect and do not lather well. Cationic detergent shampoos are excellent at imparting softness and manageability of hair. The third group of shampoos is formulated with nonionic detergents are considered to be mildest and are most popular. Most people believe that shampoos generating maximum foam are better cleansers than poorly foaming shampoos; this is not true.