Cause: Because they're made of waxes and emollients, lipsticks become unstable if they aren't kept at the right temperature, explains New York City makeup artist AJ Crimson. "If you're not storing it at room temperature, or if it gets too hot in your purse, a lipstick can melt and lose strength, which makes it more susceptible to breaking completely," he says.
Cure: Mash the bullet back into the tube and apply with a lip brush. If it's too far gone for that to work, scoop what's left into an empty lip-gloss pot, use a blow-dryer to melt it into place, and let set.
Preventive tip: If a lipstick looks as if it's melting, put it in the refrigerator for 20 minutes so it can regain its consistency.