The accessory structures of the skin include the hair, glands and nails and these develop from the epidermis in the embryo. Hair and nails serve to protect the body such as helping to retain warmth and protecting the fingers and toes whilst the glands include sweat glands which help to regulate body temperature.
Hair is most abundant in adults on the scalp, eyebrows, axilla as well as the external genitalia. Hair can also help to protect such as protecting the scalp from sunlight, and nasal hair from ingesting foreign particles such as pollen.
The skin glands include sebaceous glands, and these are mostly connected to hair follicles. Sebaceous glands secrete sebum which is an oily substance that coats the surface of the hair and keeps it from drying, and from excessive evaporation of water from the skin. Other glands in the skin include the sudoriferous glands such as sweat glands. Sweat glands helped to regulate body temperature by inducing sweating.
Nails are tightly packed plates of hard, dead keratinised epidermal cells. They cover the ends of the fingers and toes and consist of a nail body, a free edge and the nail root.
The accessory structures of the skin are in or originate from the dermis. Injecting into the dermis can be painful (due to the location of the free nerve endings) and cause bleeding (as blood vessels are located in the dermis). There are desirable and undesirable consequences of injecting the products commonly used in aesthetics procedures into the accessory structures of the skin. We will consider botulinum toxin, platelet rich plasma (PRP) and dermal filler such as when performing a facial and skin rejuvenation treatment.
Botulinum toxin is widely used for a condition called hyperhidrosis. In this procedure the injections are delivered at a superficial level (just into the dermis) with the intention of using the toxin to temporarily inhibit the release of acetylcholine, thus prevent the stimulation of eccrine sweat glands. Several randomised studies have shown that botulinum toxin type A is a safe, effective, and durable method of treating patients with primary hyperhidrosis (Doft et al 2012). There is some preliminary evidence that intradermal injections of botulinum toxin (English, et al 2022) and PRP (Oth, 2018) are an effective treatment for androgenic alopecia, however more research with larger sample sizes, randomisation and control groups is required. It’s hard to imagine that someone would inject for aesthetic purposes into the finger or toenails, this would be extremely painful and completely unwarranted. Typically, dermal filler injections are delivered either deep on the bone with a needle or with a cannula under the subcutaneous connective tissue layer. One would not typically inject into the dermis.
As with any injection, the unintended consequences include post procedural pain and redness as well transient headache, nausea and allergy if using botulinum toxin. There is the risk of infection with any procedure involving injections and aseptic non-touch technique should be used.
References
Doft, M. A., Hardy, K. L., and Ascherman, J. A. (2012). Treatment of hyperhidrosis with botulinum toxin. Aesthetic surgery journal, 32(2), 238–244.
English, R. S., Jr, and Ruiz, S. (2022). Use of Botulinum Toxin for Androgenic Alopecia: A Systematic Review. Skin appendage disorders, 8(2), 93–100. https://doi.org/10.1159/000518574
Oth, O., Stene, J. J., Glineur, R., and Vujovic, A. (2018). Injection of PRP (Platelet-rich plasma) as a treatment for androgenetic alopecia : a systematic review of the literature]. Revue medicale de Bruxelles, 10.30637/2018.17-056. Advance online publication. https://doi.org/10.30637/2018.17-056
Tortora, G. D and Derrickson, B. (2006). Principles of Anatomy and Physiology, 11th Edition. John Wiley and Sons. Page 144-170.
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