Review of hair prosthetic options for patients with alopecia

Advanced cases of alopecia can be very difficult to treat pharmacologically. Hair loss can be emotionally taxing for many, leading to depression, anxiety, or suicide. Currently, there is limited medical literature on prosthetic hair devices available for patients with alopecia.

alopecia areata, for example, are more prone to stress and tend to demonstrate symptoms of anxiety. 2 Many studies have demonstrated a negative social stigma associated with hair loss.Women are particularly vulnerable as they can place a greater emphasis on physical appearance. 3Hair loss impacts the way people perceive themselves, and the use of hair prostheses has been shown to improve this perception.A study done in 2018 demonstrated a significant improvement in self-reported competence and selfesteem in patients with severe alopecia areata after wearing wigs for ≥4 weeks. 4In a survey study of alopecia patients in the United Kingdom, 46% of participants noted that wearing a wig positively improved their life. 5It's important for dermatologists to be allies for patients with advanced alopecia by being well-versed in alternative treatments such as counseling and hair camouflaging technologies, in addition to traditional pharmacological therapies.The spectrum of hair camouflaging options is beyond the scope of this review.We will focus specifically on providing dermatologists with an up-to-date overview of hair prosthetics, colloquially referred to as "wigs."

| MATERIAL S AND ME THODS
A PubMed and online media search of the literature included the keywords alopecia, wigs, dermatology, camouflage, polyurethane, weft, cap, prosthesis, hair, net, closure, frontal, 360 degree, u-part, silk, human hair, synthetic hair, traction alopecia, folliculitis, dermatitis, lace, HD lace, central centrifugal cicatricial alopecia, scarring, hair loss, monofilament, and swiss lace.These terms were also entered into the search engine and combined using "AND" and "OR" as needed to narrow down search results.Inclusion criteria included peer reviewed articles in English discussing any of these terms in a hair-related context.

| RE SULTS AND D ISCUSS I ON
To understand the spectrum of hair prosthetics currently available, it's important to first consider the cap foundation, patterns of scalp coverage needed, the differences in cap attachment material, and the hair fiber type.

| Hair prosthesis cap foundation: Wefted versus net versus polyurethane wigs
A prosthetic cap is the base of a hair prosthesis that mimics the shape of a person's head.Caps can be removed and applied to the head as frequently as a patient desires.Hair fibers are woven into a hair prosthesis cap.The cap can be a weft, net, or a polyurethane foundation. 6

| Wefted foundation
Wefted hair prostheses, the most worn cap foundations, are also known as capless hair prostheses or open cap hair prostheses. 6A "weft" is a slender piece of cloth material in which hair strands are machine-sewn in rows to lay all in one direction.These pieces are connected to each other horizontally and run back and forth over the whole cap.Additionally, wefted hair caps have small open spaces between the wefts, allowing airflow into the scalp. 6These caps are optimal for patients who live in warmer weather.They are more ideal for patients who wear wigs occasionally or those who are not experiencing total hair loss since the parting and crown areas of the cap are more noticeable than other foundation types.The main limitation of this foundation type is lack of parting versality which makes it difficult for hair to be styled in this wig.

| Net foundation
Net or monofilament foundations are sheer mesh units made from polyester or nylon into which hair is hand knotted.Each strand is individually knotted into the mesh cap using tiny hooks.This allows the strands to move naturally and be parted in all directions.
Many caps, regardless of their main foundation can have a separate top portion (crown or frontal hair line) made from monofilament material (Figure 1).Because these monofilament prostheses are well-ventilated, they are great for daily wear in those with sensitive scalps.These wigs are ideal for patients who desire thin hairstyles because the construction of monofilament caps require less hair to be inserted into the cap.This lack of volume allows the cap to lay close to the scalp.

F I G U R E 1
Hair prosthesis constructed with both monofilament and polyurethane materials.Photo courtesy of Ewigs Toupee (https://www.etsy.com/shop/EwigsToupee).

| Polyurethane foundation
Polyurethane prostheses are custom-made pigmented prosthesis caps that mimic the appearance of skin (Figure 2).With a hand looping technique, hairs are injected into a skin-like membrane base.
Injecting hair into this base creates a decreased hair density which allows the patient's natural scalp to appear in between the hair fibers. 7,8Polyurethane prostheses can be thick or thin.The thicker foundations, although durable, are not as comfortable as net or wefted foundations because they are poorly ventilated. 7Wearing these wigs during cooler temperatures is preferable.The thickness can make the hairline look bulky and overall unnatural. 8lyurethane foundations are highly desired by patients because they can be worn as up-dos and can be parted freely.This type of wig cap can be worn without the use of adhesives because the wig naturally creates a vacuum-like seal around the head.It is important to keep in mind that full polyurethane prostheses can only be worn by those who are completely without hair since the vacuum-seal characteristic would only work on the smooth surface of a scalp.In contrast, patients may prefer combined-unit full coverage prosthetics, which have the benefit of being less expensive and offer a more natural cosmesis especially at the hairline.These combined unit prosthetics include 360-degree attachments, closures, and frontals.360-degree attachment offers a natural skin-like appearance around the perimeter of the scalp (Figure 3B).These attachments will allow patients to pull their hair upwards into a ponytail and overall comes with more versatility in styling options and freestyle parting due to the larger parting space.These attachments are not ideal for everyday wear but are desired for special occasions.The application of both 360-degree attachments and frontals (discussed later) are more complex for daily wear because they require extensive and time-consuming upkeep which is not beginner friendly.Patients would be expected to apply the attachment securely to the front and/or perimeter of the hairline with hair glue and allow for several minutes of drying time before styling the shorter hairs at the very front of the hairline.Patients also need to be careful when removing the glued attachment with a small amount of water at the end of the day to prevent breakage at the hairline.

| Closures
Closures are smaller attachments and can be sewn onto the anterior of a cap at any desired point, but most commonly to the anterior midline of the cap (Figure 4A).The attachment typically measures 4 × 4″ or 5 × 5″, although other sizes do exist (Figure 4B).
Larger closures offer more flexibility in creating deeper side parts and are more feasible for daily wear or those with busy schedules since glues are typically not necessary for them to adhere to the hairline.Additionally, there is a much smaller section to style and manipulate compared to standard frontals and 360-degree attachments.

| Frontals
Frontals are similar to closures and 360-degree attachments except they typically measure 13 × 4″ or 13 × 6″ and extend from temple to temple, which provides more robust coverage at the front of the scalp (Figure 5A,B).

| U-shaped
A U-shaped coverage prosthesis is the only partial coverage option that allows for a frontal section of the patient's natural hair to lay over the U-shaped opening for a more natural appearance (Figure 6).
The U-shaped opening can be shifted to be a midline or a side part depending on the needs of the wearer.This option would not be optimal for patients with decreased hair density or breakage at the anterior aspect of the scalp.Another downside of U-shaped wigs is that frequent heat application or manipulation of natural hair with chemicals such as perms to blend it with the texture of the wig hair can lead to hair breakage over time.

| Hair prosthesis attachment material: Silk versus swiss lace
Frontals, closures, and 360-degree hair pieces are made with hair strands that are tied and knotted onto either a silk or swiss lace base.

F I G U R E 4 (A) A traditional closure attached to anterior midline of cap. Photo courtesy of AliQueen Hair (Aliqu eenha ir.com). (B) 4 × 4″ traditional closures. Photo courtesy of BeautyForever Hair (Beaut yfore ver.com).
Both options are intended to blend in with the patient's natural skin tone in their own unique ways.

| Silk base
Silk-based hair pieces consist of two layers embedded with individual strands of hair. 9The top layer is made from silk while the second layer is a thick lace.The two layers yield a thick and opaque product.The thickness of silk-based hair pieces can lead to a bulky appearance of the hair prosthesis when applied on the patient's scalp which is one of the reasons it is less favored compared to lace-based hairpieces.However, the opaque nature of the silk top layer mimics the patient's scalp leading to a more natural look with no visible hair knots. 10lk base hair pieces are available in select colors: ivory, medium, dark.The limited color range leads to a hair piece that may not blend well with the patient's scalp in those with darker skin tones.Unlike swiss lace base hair pieces, silk base hair pieces normally require color tinting with lace dyes/tints to achieve optimum scalp color. 11though silk-based hair pieces are more expensive, they are more durable and last longer than their lace-based counterparts.

| Swiss lace base
Lace based frontals and closures, in contrast, are the most common options.Many women with both chemically treated or naturally styled hair prefer lace bases because of their adaptability to different scalp colors.Generally, the four options for lace colors are brown, medium brown, light brown, and transparent.The best color for the patient should be determined based on the patient's skin tone.
Additionally, the lace can be further manipulated with dyes or tinted with non-permanent sprays like Ebin Lace Tint to better match the lace color to the wearer's scalp.The hair knots on the lace can be bleached with bleach powder and cream developer to a golden color, allowing the lace to look even more like the roots of a human scalp.
After bleaching, a stylist can pluck the hairline of the frontal or closure with tweezers to mimic the density of a patient's real hairline.
The HD or high-definition lace is the most recent addition to the lace category.HD lace is a type of swiss lace that blends seamlessly with the scalp because it is thin, soft, and transparent, making the line of demarcation at the hairline nearly invisible compared to traditional swiss lace (Figure 7A,B).It can blend with most skin tones and does not require stylists to bleach the knots.This lace type comes with a few disadvantages.Not only is it the most expensive option out of all the lace types, the delicate material is prone to tearing after constant manipulation from tugging, brushing, and combing.Therefore, it is not recommended for daily wear.locations all over the world, especially India and China. 12Therefore, it can be dyed and combed as if it were the patient's natural hair.
Human hair is available in nearly all lengths, and textures.Standard color is brown-black hair, but true human hair is unique in that it can be dyed to any desired color.Some can last for at least a year with proper maintenance.If a patient plans to extend the life of their human hair wig (regardless of hair texture), it is important to gently wash the wigs with lukewarm water, shampoo, and a moisturizing conditioner after every 8-10 wears rather than daily or every other day maintenance.

| Synthetic hair
Synthetic hair is made from processed fibers such as nylon acetate and dynel fibers. 9Synthetic hair can often mimic the look and feel of human hair as it can be worn in pre-set curly, wavy, and straight styles.Unlike human hair, synthetic hair cannot withstand heat from hair appliances or chemicals like hair dye because of the risk of damaging the fibers.Although the durability is below that of human hair, it can still last several months with gentle care.Synthetic hair is also a more affordable option with a typical price range of $30-$100. 13

| Cons of prostheses: Traction alopecia
Although certain hairstyles help conceal hair, those same styles can exacerbate the progression of hair loss.Traction alopecia occurs when patients have hairstyles that cause prolonged tension to the hair roots.Hair practices, especially braids, twists, weaves, and hair prostheses are known to put tension on the hair.In relation to hair prostheses, the weight of the added hair, the tightness from braiding, the choice of liner, the injury sustained from gluing and heating, and the mechanical removal process can exacerbate hair damage and tractional hair loss.Traction alopecia can be prevented or minimized with appropriate education.
In the early stages, while the hair follicles are still attached, the aim is to alleviate hair tension on the scalp.The type of lining worn underneath the hair prosthesis can also increase the risk of traction alopecia.Liners are lightweight, thin materials worn over the scalp and provide a barrier between the hair prosthesis and the scalp.Unlike wig grips (discussed later), liners cover the entirety of the scalp (Figure 8A).Cotton or nylon liners pose a moderate risk in the development of traction alopecia whereas satin liners carry a low risk.Recommending satin liners over cotton or nylon wig liners could potentially reduce the risk of developing traction alopecia in patients. 14ir prostheses that are applied to the hairline via glue carry a unique concern.Because glue adhesives inadvertently make contact with hair follicles, hair breakage may ensue upon removal of the hair prosthesis. 14Another potential adverse reaction to hair prostheses includes both occlusive and mechanical folliculitis.

Full
coverage prosthetics are good options for individuals with alopecia affecting the whole scalp.Hair prostheses can offer full scalp coverage via a single unit or two or more units.In a single unit prosthetic, the previously mentioned foundations cover the entirety of the scalp, front to back and temple to temple.The base of these prosthetics is typically composed of one cap that does not require any attachments.
3.2.2| 360-degree 360-degree attachments are used in conjunction with a central cap to provide robust coverage for the entirety of the scalp (Figure 3A).The F I G U R E 2 Polyurethane prosthesis.Photo courtesy of Ewigs Toupee (https://www.etsy.com/shop/EwigsToupee).F I G U R E 3 (A) Front view of 360-degree prosthesis covering entirety of scalp.Photo courtesy of AliQueen Hair, (Aliqu eenha ir.com).(B) Lateral view showing an inside-out 360-degree prosthesis spanning the perimeter of head.Photo courtesy of BeautyForever Hair (Beaut yfore ver.com).

3. 5 |
Wig hair fibers: Human versus synthetic 3.5.1 | Human hair Human hair prostheses look and feel like human hair and are therefore recommended for patients who are looking for styling versatility.Human hair is normally obtained via hair donations from F I G U R E 6 U-shaped prosthetic allowing for natural hair to be pulled through an opening.Photo courtesy of BeautyForever Hair (Beaut yfore ver.com).F I G U R E 7 (A) HD lace when placed on scalp.Photo courtesy of BeautyForever Hair (Beaut yfore ver.com).(B) 4 × 4″ closure covering with a brown swiss lace base.Photo courtesy of BeautyForever Hair (Beaut yfore ver.com).
Glue adhesives can occlude follicle openings which can lead to obstruction and inflammation.Tightly fitted hair prostheses and friction can lead to mechanical folliculitis.Maintaining proper F I G U R E 8 (A) Cotton liner covering entirety of scalp.Photo courtesy of Bold Beauty Hair (etsy.com/ie/shop/BoldBeauty Hair).(B) Silicone wig grip placed along perimeter of the scalp allowing for firm adhesion of prosthesis.Photo courtesy of Bold Beauty Hair (etsy.com/ie/shop/BoldBeauty Hair).