While color separation is one sign of age, Wang says it's important to look for other changes in a nail polish's color and texture. If the hue has changed since you bought it or it looks thick and gloopy, it's likely past its prime. Another huge red flag is odor, adds Berry.

OPI is a leader in nail polish brands. It's more expensive than other brands because of the quality of the polish. I like OPI polishes however, my go to brand of nail polishes is Zoya. You get what you pay for and I believe OPI is one of the best nail polishes that's comapred to China Glaze and Essie.