As an expert in clean beauty and skincare, I can provide you with some guidance on determining if a shower gel has expired. Here are a few indicators to look out for:

1. Expiration Date: Check the packaging or bottle for an expiration date. Many shower gels have a specific date printed on them, which indicates the manufacturer's recommended shelf life.

2. Change in Appearance: Observe any changes in the shower gel's color, consistency, or texture. If it appears discolored, separated, or has developed clumps, it may be a sign of expiration.

3. Unpleasant Odor: Take note of any unusual or foul smells coming from the shower gel. A strong, rancid, or off-putting odor could indicate that the product has gone bad.

4. Irritation or Allergic Reactions: If you notice any skin irritations, redness, itching, or allergic reactions after using the shower gel, it could be a sign that the product has expired or become contaminated.

5. Storage Conditions: Improper storage can accelerate the expiration process. If the shower gel has been exposed to excessive heat, sunlight, or moisture, it may deteriorate more quickly.

Remember, using an expired shower gel may not only result in reduced efficacy but could also lead to skin irritations or infections. It's always best to err on the side of caution and replace any products that show signs of expiration.