When summer arrives, people with oily hair often face a daily struggle: hair that looks clean in the morning turns greasy and flat by the afternoon. The airy, voluminous look you tried to create collapses into limp strands in just a few hours. This is especially common for those with oily scalps and fine hair, leading to a frustrating cycle of “the more you wash, the flatter it gets.” The wrong shampoo can make things worse by accelerating oil production and weighing down the roots. In hot and humid weather, choosing the right shampoo — one that is refreshing but not drying, oil-controlling yet volumizing — is key to keeping…