Hair is seen as a fashion accessory, and the beauty industry has armed consumers with a wide range of products and tools (both at home and in salons) that can change hair’s colour, shape and texture. Colouring and straightening hair are two common beauty practices, but using such hair products properly and safely is vital to avoid hair blunders and adverse reactions.

The following sections offer detailed information for some common questions and different elements of hair care.

Shampooing the Scalp
Depending on one’s hair type, shampooing frequency may vary from daily to only once per week.  Generally, straighter hair types tend to get oilier than curly to kinky hair types.  Even if one does not require daily use of shampoo, it is helpful to wet or dampen the scalp every few days to avoid buildup of dust, dirt and other environmental debris on the scalp.

Handling wet hair
Use of a hair conditioner facilitates combing when hair is wet. For hair that tangles, use a wide-toothed comb and begin combing from the ends, slowly working your way up towards the scalp. Avoid vigorous towel-drying or harsh combing and brushing of wet hair, since wet hair, although elastic, can break more easily than dry hair.

Styling products and other chemicals
Chemicals in colouring, perming and relaxing products permanently weaken hair and make it more prone to breakage. Avoid applying these products to hair that is already damaged.

Too much brushing
Backcombing and overbrushing can cause split ends. Split ends make hair prone to breakage further up the hair shaft.  The remedy for split ends is trimming the hair.

Tension-based hair styles & Tying hair up in a style with tension
Braided styles such as cornrows, microbraids, box braids, slicked buns and tight ponytails and any style that causes pulling can stretch or tear hair, causing breakage and dislodge hair from its root. Regularly wearing hair in a tight style can lead to traction alopecia, hair loss caused by pulling on the scalp.  While it most commonly occurs along the hairline of the scalp, it can truly occur at any site of the scalp that is subject to tension or pulling.  It is a reversible form of hair loss initially.  When it recurs over several months, it can result in permanent hair loss.

Extensions, Weaves and other Added Hair styles
Women, and sometimes men, use extra hair to achieve a specific look, or to give the appearance of fuller hair.  These styles can pull on or damage the existing hair. When used with glue, the existing hair can tear, or there may be an irritation or allergic reaction to the glue that occurs on the scalp.  It is advised to limit use of these styles and allow for ample time for the hair to be free of extensions/ weaves / hair styles with added hair.

Oily hair indicates an oily scalp. Hair follicles are associated with oil-producing glands that produce sebum (oil) naturally. The more oil produced, the greasier the hair.  The less that oil gets removed with shampooing, the more oil builds up on the scalp and the hair.

Seborrhea is the oily skin/scalp condition present when the glands produce too much oil. This can be caused by excessive activity of sex hormones – androgens – and contribute to forming acne or seborrheic dermatitis. Washing hair more frequently, depending on one’s hair type, helps to reduce oil on the scalp.  Avoid applying oil directly onto the scalp as it can accumulate on the scalp and even attract forms of yeast.  A doctor may also recommend therapy in the form of retinoids, topical or oral to reduce seborrhea, or hormone therapy to reduce androgen activity to decrease sebum levels.

Chemical Relaxers

Hair relaxers are used to chemically straighten curly or wavy hair. Use is not recommended more frequently than every 8 – 12 weeks, depending on the rate of one’s hair growth.  Check with a salon professional about how often you can safely use a hair relaxer; overuse may weaken and damage hair, or burn your scalp. Products sold over-the-counter are called ‘no-lye” relaxers and contain guanidine hydroxide.  Lye relaxers are less commonly available and contain sodium hydroxide.  Both types of relaxers lead to permanent hair straightening and can damage the hair or scalp.

Using relaxers more safely

To minimize damage to the hair or scalp when using hair relaxing products:

  • Apply petroleum jelly to scalp as added protection before using relaxer
  • Do not apply relaxer directly to the scalp; apply it to non-straight “virgin hair”
  • Do not use on freshly washed scalp/ hair.
  • Follow directions exactly; never leave relaxer on longer than instructed
  • Get help in applying and rinsing.  Ensure the relaxer has been rinsed out thoroughly.
  • Use a neutralizing shampoo
  • Do not use hair dye the day of, or within 2 weeks of relaxing the hair.
Hair Smoothing

Keratin Treatments – Used increasingly over the last 10 years, these are salon-offered treatments that are performed on loosely curled, wavy, or straight hair. They contain formaldehyde and are used to provide a straight pattern to the hair shaft which results in a smoother hairstyle with blow-drying the hair. Health Canada has identified several salon-based keratin treatment products that contain excess formaldehyde. Formaldehyde is permitted in levels of 0.2% or lower in cosmetics, and is a preservative in several products. It has been cautioned that formaldehyde is a sensitizer that can vapourize when heat is applied to the hair (e.g. blow drying and ceramic straightening). The adverse effects associated with these treatments include burning of mucus membranes (eyes, nose, and throat), breathing difficulties, and even hair loss

Hair colouring products range from temporary to permanent formulas. Both home and salon-quality products have evolved to less harsh formulas, but there are still risks. Problems can include burning, itching and/or scalp redness, hair loss and severe allergic reactions that could involve facial swelling and trouble breathing.

Reaction after use of hair dye? There are 2 main types of reactions that can occur on the skin:
  • Irritant dermatitis – This can occur quickly after hair-dying (within hours). You may experience redness, irritation, burning or itch. This may occur in proportion to the amount of hair dye used.
  • Allergic contact dermatitis – this reaction occurs after a delay (2 – 3 days after use of hair dye). It can result in redness, flaking, itch, and even blisters along the hairline, neck, ears.
    • Allergy to paraphenylenediamine (PPD)? If you use permanent hair dye, you need to know about PPD since this chemical substance is often present in hair colouring products, even henna-based products. Typical adverse reactions include dermatitis (irritated inflamed, scaling, itchy skin at/ near the site dye was applied). Severe allergic reactions can lead to urticaria (hives) — or even anaphylaxis, a potentially fatal reaction. It’s important to perform a patch test each time you use a hair dye, even if you’ve used it before, since an allergic reaction can develop at any time.
Hair Dying Tips

For safer use of hair colouring products:

  • Read – and heed – all directions and warnings
  • Always do a patch test before using any hair colouring product
  • Never use hair dye on eyebrows or lashes; it may cause blindness
  • Always wear gloves when applying dye
  • Don’t leave product on hair longer than directed
  • Be sure to rinse scalp well to remove all hair dye product


Hair Care Article

J Cosmet Dermatol. 2012 Mar;11(1):9-16.