Thanks for reaching out to us and for your interest in our products! Some of our products do not have a seal on them as our products are factory sealed and mechanically tightened to the right specification to avoid leakage. Some of our products have a disk in the top of the cap that also protects it from leakage and product spoilage.
Additionally, it does not improve the integrity of the product to have a seal and our products have very strict quality control parameters and strict expiration dates that the seal is again not warranted.
Please let us know if we can help you further, and remember, a good hair day can change the world!