If you have ever waxed, shaved, or plucked hair from your body, you are definitely acquainted with ingrown hairs and how they can be itchy, painful, and irritating in some cases. This article will discuss what are ingrown hairs, how to prevent them, and which hair removal treatments are more suited for avoiding ingrown hairs
What are ingrown hairs and why do we get them?
The medical term for ingrown hairs (Figure 1) is pseudofolliculitis but they are also known as “shaving bumps” or “razor bumps”. Ingrown hairs are usually formed in areas of the skin where the hair is thick, such as underarms, legs, and beard and pubic areas. Pseudofolliculitis can form in both women and men but is especially frequent in black men who tend to daily shave their facial hair. Additionally, hair structure and growth direction are important factors in ingrown hair formation (curled hair is thought to facilitate the reentrance of the hair back into the skin and shaving leaves sharp edges in hairs enabling easier skin penetration) [1,2].
An ingrown hair forms when the tip of the hair shaft, instead of fully exiting the skin’s surface, reenters the skin and remains embedded, commonly leading to inflammation. Symptoms include:
Small, rounded bumps (papules)
Small puss-filled blisters (pustules)
Figure 1. Ingrown hair: a) Extrafollicular penetration (after being cut, hair regrows back towards the skin and penetrates it leading to inflammation); b) Transfollicular penetration (after being cut, hair regrows towards the follicular wall and enters skin’s dermis) 
Accumulation of dead skin cells after hair removal is a factor contributing to the formation of ingrown hairs. Trapped underneath the skin, hair gets infected and can form first papules and as they swell- pustules. Even though trapped hair remains underneath the skin, the hair growth cycle is not stopped. As more hairs grow, the old hairs are pushed deeper into the skin. Skin inflammation continues until the hair is removed or grows out of the skin completely . Scratching and/or picking ingrown hairs can disrupt the skin surface and facilitate the entrance of bacteria leading to the formation of pus, very similar to acne .
How can we prevent the formation of ingrown hairs?
In severe cases of ingrown hairs, patients are advised to avoid tweezing, shaving, and waxing (for men- growing a beard, cutting it with scissors, or using other alternatives such as electric clippers). In most other cases ingrown hair prevention is achieved usually with certain treatments prior to and after hair removal treatments. Exfoliating the skin helps remove the build-up of dead cells at the skin’s surface and opening the pores and follicles which helps in the prevention of hairs re-entering the skin. Opposed to shaving, waxing eliminates entire hair follicles and may decrease the possibility of the formation of folliculitis, but not necessarily. Shaving increases the possibility of hairs curling back into the skin and the formation of ingrown hair. Exfoliation is recommended every 2 to 3 days between shaving and waxing to avert re-entrance of hair into the skin . One of the most common exfoliating agents used is topical glycolic acid. The results reported in one study comprised of two placebo-controlled trials (35 adult men) have shown that glycolic acid lotion was much more effective in treating pseudofolliculitis compared to placebo (more than 60% of reduction on the treated skin side was observed which enabled everyday shaving regimen for patients). Other topical medicinal treatments include benzoyl peroxide, topical retinoids, topical antibiotics, and low-potency topical corticosteroids . Additional tips that can help prevent ingrown hairs are:
Using lubricating shaving cream or gel in order to make hair softer (or apply warm cloth).
Every time you shave use a sharp razor.
Avoid pulling your skin while shaving.
Rinse the razor after each stroke.
Try to shave in the hair growth direction.
When finished, rinse your skin and apply aftershave/moisturizer. 
Which is the best hair removal treatment to avoid ingrown hairs?
In recent years, another option for the removal of unwanted hair has been developed as highly efficient and (nearly) permanent which uses light of certain wavelengths. The energy of light is transformed into heat that impairs the tube-shaped sacs inside the hair follicles which produce hairs. These treatments can be divided based on the type of light is used: IPL (Intense Pulsed Light, broad-spectrum pulsed light) or Laser (a more concentrated beam of light, different subtypes: diode, Nd: YAG, alexandrite, and ruby) 
Figure 2. Lumea IPL series 9000 
Both methods have their advantages and disadvantages. For example, IPL can be used at home but provides only a decrease in hair growth, not permanent hair removal compared to Laser. On the other hand, Laser must be used by a professional and is much more expensive compared to IPL. The good news is that both treatments significantly decrease the risk of ingrown hairs and provide solutions for patients who suffer from this reoccurring and painful condition .
If you are interested in finding out more about light hair removal treatments, feel free to check out "Shedding light on hair removal: IPL vs Laser" by Cathy and Sara as well as our other articles about hair such as: "The science behind hair conditioner", "The science of damaged hair" and "The science behind hair graying".
https://www.mayoclinic.org/diseases-conditions/ingrown-hair/symptoms-causes/syc-20373893 [Accessed 25.03.2021.]
 Patterson, Cole: "Fighting Folliculitis: Overcoming Ingrown Hairs, Razor Bumps & More" Dermascope Magazine Mar. 2020 https://coleskincareformen.com/blogs/news/ingrown-hairs [Accessed 25.03.2021.]
 Kern, Dan: “What Are Ingrown Hairs?”
https://www.acne.org/WhoIsMostLikelytoDevelopIngrownHairs? [Accessed 25.03.2021.]
 Perricone NV. Treatment of Pseudofolliculitis Barbae with Topical Glycolic Acid: A Report of Two Studies. Cutis. 1993, 52(4), 232-235.
 Chi, C. & Fernandes, S.C.: Shedding light on hair removal: IPL vs Laser https://www.emotion-master-studentproject.eu/post/shedding-light-on-hair-removal-ipl-vs-laser [Accessed 28.03.2021.]
 https://www.philips.it/c-m-pe/rimozione-dei-peli-superflui/lumea-ipl [Accessed 29.03.2021.]