Can hair-loss concealers "suffocate the follicle"? What are the potential side-effects?

Hair is dead, so you really cannot "suffocate" the hairs. You can use concealers safely. If you have issues see a doctor for an exam.

It is a myth that hair loss concealers cause damage to the hair. These are usually organic or synthetic keratin fibres which are applied on the scalp and cover your scalp. They do not have any interaction with the hair follicles. Why people feel so ( concealers causing hair loss) is because the underlying condition i.e. Androgenetic Alopecia keeps on progressing in the absence of the medical treatment and the person feels that it is the hair fibre which is causing the hair loss.

It's a myth that these agents suffocate the hair follicle. Hairs don't need to 'breathe' - they get they oxygen and nutrients from blood vessels deep down below in the skin rather than from diffusion up above. Topical keratin based hair fibers are safe. Rarely, they irritate the scalp and rarely some of the dyes cause problems. But these are fairly rare products.  Most individuals who use these products have genetic hair loss - which is a progressive condition. Generic hair loss gets worse over time if it is not treated.  A lot of people using topical fibers will notice their hair is getting worse and worse. Not from the fibers, but from the natural progression of genetic hair loss. We've outlined all the side effects of these topical camouflaging agents in our 2008 paper published in the Dermatology Online Journal.   A link is below.Hope this information helps.

There are many myths and urban legends about hair loss, particularly on the internet, and this is one of the more persistent ones.  Hair gets its oxygen from its blood supply at the bottom of the follicle, underneath the skin, not from the top!  Hair fibers are safe and harmless for the most part.Do me a favor though - now that you know your ongoing hair loss is not caused by the hair fibers, act to prevent the relentless loss!  Don't just wait for it to happen and then expect a hair surgery to "fix" you, because that is not how it works.  Hair surgery is best as an adjunct - working WITH therapies like finasteride, minoxidil, LLLT and ketoconazole/zinc shampoos - NOT all by itself!  You will look better in the long run and your surgeon will be able to get a better result for you if you keep as much hair as you can in the first place.Good luck!