Hydrotherapy is generally safe when conducted under the supervision or guidance of a physician, but it does carry some risks: 

• Pool. In some cases, an inappropriate water temperature may produce unwanted effects in the body. Patients who are unable to swim need to wear a life vest or other flotation device (or receive supervision) to avoid the potential for drowning. Pool therapy should not be undertaken by patients who have bowel or bladder incontinence, open wounds or sensitivity to certain chemicals.

In addition, exercise performed in a pool is not weight-bearing. This means that patients who exercise in pools are not building bone mass, which is critical to helping protect against conditions such as osteoporosis, a bone-thinning disorder that is most common in women after menopause.

• Hubbard tank, whirlpool and sitz bath. Inappropriate water temperature can cause unwanted side effects in the body. For example, too much time spent in hot water can increase blood pressure. In addition, researchers have found that many recreational whirlpools have bacteria that can cause conditions such as urinary tract infections, skin infections and pneumonia.
  
  
• Sauna and steam bath. Use can be dangerous or inappropriate for many individuals, such as those with heart conditions, impaired circulation or sensation (e.g., from diabetes), acute rheumatoid arthritis, acute infections or sexually transmitted diseases.
  
  
• Damp hot packs. Improper use can cause burns.