Effect of Humidity on Human Hair

Humidity is an almost universal catalyst for frizzy or uncooperative locks--regardless of hair type. During periods of high humidity, even people who normally lack frizz-factor might combat dry, unmanageable, fluffy ends. Although moisture-laden air alone can create bad hair days, often those unpleasant frizzy or limp and unappealing effects are caused by the combination of humidity and other dynamics. Tame your mane by learning the effects of humidity and you’ll be able to sail through even the sultriest days with hair happy confidence.

During those hot sticky days when the heat index climbs, your hair is reacting to humidity via molecular changes. Hair is largely hydroscopic, or able to exchange water molecules with moist or dry air. While dry air will drive water molecules from your hair into the environment, humidity has the opposite effect on hair. The hydroscopic nature of hair during humidity will prompt absorption of airborne moisture, which in turn causes swelling of the hair--as much as 16 percent of the diameter in high humidity. This density change can account for many unsavory or unexpected styling issues. “Almost all properties of hair--including ease of styling and manageability--are determined by its hygroscopic properties,” says hair care experts Wella Professionals.

Once humidity takes its toll on hair, prompting moisture absorption, individual responses to this process begin to become apparent. While each hair type responds differently to moisture vapor’s effects, even various strands on the same head can react unpredictably. Proteins in hair aren’t uniform, with two types--the orthocortex and the paracortex--reacting differently to water molecules. Cosmetic scientists at The Beauty Brains.com, offer this explanation, “The problem is that these areas absorb water differently, so they don’t swell the same. One part may absorb a lot of moisture and swell a lot, while the other stays relatively the same.” Uneven absorption can cause twisting or bending, which can take the curl out of fine hair strands, or alternately cause frizzy effects, depending on your hair type.

Hair that is naturally curly, when exposed to humidity, will often curl excessively or be prone to frizziness, even if it has been meticulously straightened before stepping outdoors. Because curly tresses have rougher cuticles to begin with, brushing or touching hair should be avoided or minimized when it’s humid as you’ll invoke friction, which only further intensifies fuzzy locks. You may find it's better not to fight curls and allow hair to air dry naturally or spin tresses into braids on sultry days.

Flat fine hair is a factor for many women on humid days due to the weight of absorbed follicle moisture.You can rev up tired hair by opting for a volumizing shampoo and conditioner. Keep styling products lightweight during summer months. Although limp from the crown, some women experience a thickening of their hair, which may require styling changes when it's humid. If your hair is fine and wavy, allowing your hair to be loose and natural may be your best humid weather option.

All hair retains some natural water, even if it feels a tad dry. But while healthy hair generally keeps about 15 percent of water weight and in humid conditions can retain roughly 30 percent total moisture- damaged hair is another story. Excessively dry, damaged and rough hair can respond terribly to humidity due to extremely porous strands. Curl chemist Tonya Mckay Beckeer of Naturally Curly.com notes damaged hair is capable of retaining up to 55 percent water from the atmosphere, a factor that produces unrelenting frizz, puffy locks and dullness.

Surviving humid days free of bad hair days requires simple, but necessary maintenance. Keeping hair conditioned will prevent unwanted excess water vapor absorption and lessen fluffy or uncooperative locks. Make sure you use a weekly deep conditioner that packs humectants and protein-rich vitamins. Get a good trim to remove split ends, which turn frizzy in humidity. Use a silicone-based sealer or employ a smoothing anti-frizz styling product to damp hair to keep humidity from entering hair. Avoid the sun’s rays, which can provoke drying and damage that only invites tress trouble. Cover hair or spritz on a UV protecting spray when in the sun.