Insect repellent can expire, but it typically takes several years to lose its effectiveness. Most insect repellent manufacturers do not put an expiration date on their products unless the repellents expire in under 3 years. Consumers should avoid storing repellent in extreme hot or cold temperatures to maintain effectiveness.
In the absence of an expiration date, there are several ways to figure out whether insect repellent is expired. The product manufacturer can provide the expiration date. The repellent itself can also be assessed for damage, such as rust or a missing lid. If the repellent has previously been used, the consumer can spray the repellent to make sure it smells right.