Regular spa hot tubs only maintain water temperature, while hydrotherapy spa hot tubs focus on the combination of water flow and air pressure. If you want to achieve a therapeutic or deep relaxation effect with a spa hot tub, a regular model is difficult to achieve, while a dedicated hydrotherapy spa hot tub is the true hydrotherapy equipment.

Most countries and regions have clearly defined maximum temperatures for hydrotherapy hot tubs. The U.S. Consumer Product Safety Commission (CPSC) recommends a maximum temperature of 104 degrees Fahrenheit to balance comfort and safety.

Hot Tub Folliculitis (or Hot Tub Dermatitis) is a skin infection syndrome caused by contact with a contaminated hot tub. It is usually caused by a bacterium called "Pseudomonas aeruginosa". When people soak in a poorly maintained or inadequately disinfected hot tub, the bacteria enter the hair follicles or the stratum corneum of the skin.

Children over 2 years old: Can soak briefly in a specially temperature-controlled hydrotherapy hot tub. Water temperature not exceeding 37.5°C (99.5°F); time limited to 5–10 minutes; adult supervision is required.