Wear sunscreen does bad because he stops protecting the skin of the sun's rays in an effective way, as well as irritations or allergic reactions. It is recommended not to wear sunscreen.
Cosmetics and dermatological products, such as sunscreen, out of date, lose effectiveness of its components, failing to make the desired effect of protecting the skin from ultraviolet rays.
The compounds present in their formulation are subject to degradation and when stored for longer than indicated on the package may favor the appearance of microorganisms such as fungi and bacteria. These altered substances can cause dermatitis, swelling, blistering and redness, as well as injury to the cornea if used near the eyes.
These compounds may also undergo oxidation due to contact with air, temperature and light. Once oxidized, the molecules of the product transform and become irritating and allergenic.
The manufacturer himself no longer guarantees the safety of the sunscreen, if it is used after the deadline.
For all these reasons, the Sunscreen should not be worn if out of date because it can harm your health.