The answer to 'deep cleaning smells bad' is that a deep cleaning that leaves a bad odor is often caused by trapped moisture, mold, or bacteria in hard-to-reach areas. This can happen when carpets, upholstery, or other surfaces are not properly dried after cleaning. The smell may also be due to the cleaning products used, especially if they contain harsh chemicals.
To solve this issue, make sure to thoroughly dry any wet areas after cleaning and consider using more natural, eco-friendly cleaning solutions. If the smell persists, it's best to call in a professional cleaning service to properly identify and address the root cause.