Humidity typically causes frizz and alters hold due to the way moisture in the air interacts with hair. When there is high humidity, the moisture can penetrate the hair shaft, which changes the hair's structure and leads to an increased volume and texture changes. This often results in frizzy hair because the cuticles, which are the outer layer of hair strands, can swell and become uneven, causing the hair to lift and create that frizz. Additionally, high humidity can affect the styling products used, causing them to lose their effectiveness and altering the overall hold of hairstyles.
The other options do not accurately reflect the effects of humidity on hair. For instance, while high humidity can enhance shine temporarily, it usually results in less manageable hair overall. Keeping styles intact is often more challenging in humid conditions, as the moisture in the air can lead to styles falling flat or becoming unruly. Lastly, while some might think humidity makes hair easier to manage due to natural moisture, it generally complicates styling rather than simplifying it.