When the pH of a shampoo is too high (= too alkaline) it will have some not-so-great impact on your scalp and hair. A shampoo with too high pH will strip your scalp from natural oils, increasing the risks of irritation and dryness. This dryness can even lead to flakes or make it worse if you've already got dry flakes. Or for some people, the irritation will push the scalp to produce more oils, which can result in dandruff or even more regular shampoos. Plus, a high pH can mess with your scalp's acid mantle—that's the slightly acidic barrier that keeps bad bacteria at bay—so you could be looking at more irritations or even infections. Regarding your hair strands, imagine your hair cuticles as tiny tiles on a roof. A shampoo with too high pH makes those tiles stand up, which leads to your hair getting all frizzy and tangled. It also steals away the shine, leaving your locks looking dull. And if you keep using it? Well, those lifted cuticles can make your hair weak and prone to breakage over time, which you really want to avoid if you're wanting to grow long and healthy hair.