Hot pack

“Hot pack” is a general term for pouches that transfer heat to the body. They can be divided into several types based on their shape and how they generate heat.

• Disposable hot packs — When you open the packaging and shake the pack, the iron powder inside reacts with air and slowly releases heat. They are handy to carry outdoors in winter or on your commute.
• Microwavable pouches — Pouches filled with grain or gel are heated in a microwave. They are reusable and conform well to the contours of the body.
• Hot water bottles (tangpa) — This is a traditional method: a bottle filled with hot water is placed under the bedding or on the abdomen.
• Electric heating pads — These plug into an outlet and let you adjust the temperature.

Heat first warms the shallow tissues close to the skin. Rather than directly heating deep inside the body, hot packs are therefore used to provide a soothing feeling of warmth and relaxation in the area where they are applied.

Warm stimulation temporarily increases blood flow to the area and gives tense muscles a feeling of easing up. Warmth is also described as changing the response of the sensory nerves that carry pain signals, helping reduce the feeling of aching. This is why hot packs are often used for a tight neck and shoulders after prolonged sitting, a stiff lower back in the morning, or an abdomen that feels cold. In contrast, cold is more commonly applied to areas that are swollen and warm to the touch, as discussed in Heat and cold therapy.

Hot packs provide either moist heat or dry heat. Moist heat contains moisture, as with a hot pack wrapped in a damp towel, while dry heat comes from sources such as a dry towel or an electric heating pad. At the same temperature, moist heat tends to feel warm more quickly, so a layer of damp towel is sometimes added when a deeper feeling of warmth is wanted. Dry heat is useful for longer applications without dampness.

1. Wrap it in a layer of fabric. Rather than placing the hot pack directly against your skin, put it over a thin towel or clothing. This allows the warmth to spread gently and feel more comfortable. 2. Use 15–20 minutes as a guide. Once it cools down, it is fine to take a break, reheat it, and apply it again. Hotter is not better. A temperature that feels “slightly warm” is the most comfortable. 3. Move it from place to place. Leaving it in one spot for too long can make the skin red and cause stinging. Try alternating between your shoulders, lower back, and lower abdomen. 4. Pay closer attention to areas with reduced temperature sensation. Areas with dulled sensation, thin and sensitive skin, or poor circulation feel heat less readily, making it easy to leave a pack in contact for too long without realizing how hot it is. Even heat only slightly above body temperature can damage the skin with prolonged contact; this is called a low-temperature burn. Be especially careful about falling asleep with a disposable hot pack attached or using one together with bedding or an electric heating mat. 5. Try gentle movement once the warmth has helped you relax. When the hot pack has eased stiffness, slowly turning your neck or straightening your lower back can make movement feel much easier.

If the skin where you applied the hot pack becomes blotchy and red or develops blisters, and a stinging sensation lasts for several days, the heat may have been too intense. Try lowering the temperature or adding another layer of towel. If swelling and warmth keep getting worse after application, or the pain increases, it is time to stop applying heat and take a closer look at how your body is doing.