There has been previous research suggesting cold has an effect on pain relief, however there is limited knowledge on the relationship between exposure time of a cold stressor and how long it takes to return to homeostatic temperature and normal response to cold, in addition to whether location site affects this. The skin's thermal response to a cold stimulus is not fully understood. This provides precedent for potentially using cold stressors as a way to provide pain free injections.

5 participants will be exposed to a block of copper on the skin at -2°C for 30 seconds, and a thermal camera will be used to identify the amount of time it takes for the skin to return to its homeostatic temperature. The participant will then be left for 30 seconds before the experiment is repeated to identify if there is a change in the response to cold after the first exposure.

If increased sensitivity in the response to cold occurs, the experiment will be repeated by adding an additional 30 seconds between repeats to identify the minimum time required between exposures that doesn't result in increased sensitivity. This will occur until there are two consecutive times with no increased sensitivity.

This will occur on both the forehead and on the deltoid of the arm, two areas where injections are common.

The cold stressor will be block of copper metal which will be cooled to this temperature.

A thermal imaging camera is used to identify the 'normal' temperature of the skin on the forehead. A cooled block of copper is then placed onto the skin of the forehead at a temperature of -2°C for 30 seconds. A timer is then used to measure how long it takes for the skin on the forehead to return to its normal temperature. This is then repeated twice with a minute in between each measurement to identify if there is a change in the response to cold, where it takes more/less time to return to normal levels. If the time taken to return to normal changes, the participant will be given 30 minutes to rest, and then repeat the experiment with an additional minute between repeats. This will continue until there is no change in the amount of time it takes for the skin to return to normal on the forehead once exposed to the cold conditions to identify a sensitivity time due to a change in the response to cold. This will be tested on 5 patients.

This will also be tested on the outer deltoid, where injections usually occur in your arm.

Inclusion Criteria:

• Able to give informed Consent
• Above 18 years old

Exclusion Criteria:

• Skin conditions or irregularities, or on medication that affects temperature regulation

Not planned