Is your hair constantly dry? Does it have trouble reacting to products? Does it frizz easily? Am I preaching your gospel right now? Well, its porosity could be at the root of the problem."Hair porosity" is a term I've heard thrown around on the internet more and more recently. In a nutshell, it's your hair's ability — or inability — to absorb moisture. It's mostly of concern for those with curly and tightly coiled strands — whose manes are notorious for being persistently parched. When it comes to natural hair, knowing your specific porosity is important because, simply put, it will help you better understand your hair. Diane C. Bailey, celebrity stylist, author, and SheaMoisture beauty ambassador, tells us: "Identifying your hair porosity is important to achieve your healthiest hair possible. Knowing your hair porosity helps you determine what ingredients and products are best."There are three porosity types: low, medium, and high. Typically, hair with high porosity is prone to damage, breakage, and gaps, Bailey explains. This allows the hair to absorb moisture quickly but also release it just as fast. "Highly porous hair tends to look frazzled and feels dry and coarse," she says. Low-porosity hair, on the other hand, has a tendency to be on the stubborn side. This type experiences buildup, and has trouble retaining moisture and absorbing natural oils. Basically, products sit on the hair, and your tresses take a longer time than normal to dry. It might look healthy on the outside, but it lacks in the elasticity and volume department. Strands that fall in the middle take in and hold moisture for a good amount of time (a.k.a. The Dream).For most ladies and gents, porosity is genetic, but elements like environmental stresses, hard water, heat-styling, and chemical treatments can also affect where on the scale your strands lie. A classic way of determining whether your hair veers on the low or high end of the spectrum is the old hair-in-a-cup-of-water trick, says celebrity hairstylist Lacy Redway . "Some women like to test their strands by dunking one of their freshly cleaned loose strands in a cup of water to see if it floats or sinks," she explains. She adds that using clean hair is important, as dirty strands will alter your results. "If your hair sinks quickly, it's high in porosity. If it floats, it's low-porosity. And if it takes longer than a couple of minutes to sink, you most likely have medium porosity." Bailey also suggests checking out SheaMoisture's Porosity 411 website , which will help you nail down your type (and recommend products) after you answer several questions.