A permanent wave, more commonly known as a perm, is a hair procedure that uses chemicals to change the shape of the hair follicle from straight to curly, according to the website Hair Boutique. Tightly-curled perms were especially popular in the 1980s, but went somewhat out of fashion until recently. Many hair salons now offer perms that add loose curls or waves to the hair rather than the traditional corkscrew curl.
Perms create curls that typically last three to five months. After three months, the website Easy Curls recommends re-perming your roots to prevent your hair from looking flat on top. A perm usually takes one or two hours, but you won't see the full effect for approximately 24 hours. In this "settling" period, do not get your hair wet, because this can affect the chemicals and ruin the perm.
The chemicals used in a perm change the shape of the hair follicle to create curls. This can damage hair, leaving it dry. Using hair products designed for permed hair can help protect your hair and minimise the damage, according to Salon Web, the website of Sunset Hair and Beauty in Tennessee. Regular trims to remove frazzled ends can also help keep permed hair looking healthy.
Certain types of hair are more prone to damage caused by a perm, according to the website Target Woman. Women with coloured hair should reconsider before getting a perm, because the build-up of chemicals from both processes can seriously damage hair. Target Woman recommends colouring hair after a perm, rather than before, to minimise damage.
Certain factors can affect the perm's ability to take to your hair, according to the website Hair Finder. Certain narcotics such as methamphetamines can prevent your hair from holding a curl. Prescription drugs such as Retin-A can also prevent your perm from sticking. Pregnancy or menopause often reduces the length of time it takes for the chemicals to work on your hair. Other factors that prevent hair from holding a curl include past anaesthesia, and regularly taking iron supplements.