Injections are associated to a certain level of pain which tolerance can vary between individuals. As regards non-invasive pain control techniques in subcutaneous injections, scarce literature exists with adequate levels of evidence and design quality to support any specific analgesic method.

In this study, the investigators evaluated the effectivity of three non-invasive analgesic techniques (cold, anesthetic cream and vibration) when performing subcutaneous forehead injections, in a series of 100 healthy volunteers.

This study is a randomized, controlled, simple-blind clinical trial, and it has been approved by the Ethics Committee of the Medical Research Institute Hospital La Fe. The study included 100 healthy volunteered, and it was performed in the University and Polytechnic Hospital La Fe, Valencia.

The procedures of the study consisted in the sequential performance of four injections of 0,1mL of physiologic saline (0,9%NaCl) in the forehead of each subject, 2cm above the eyebrows, with a 29G needle, after applying any of the non-invasive anesthetic methods studied in the trial, except for the control zone. The anesthetic method utilized in each part of the forehead of each patient was randomized through simple randomization. Injections always started from the right side of the forehead to the left. The non-invasive analgesic methods utilized were:

• Control zone: None
• Vibration: Application of the vibrating device on the skin below the injection site, before and during injection.
• Cold: Application of a bag of 50mL of frozen physiologic saline covered with a plastic glove on the injection site for 50 seconds prior to performing the injection.
• Anesthetic cream: Application of a uniform thickness of 2mm of the anesthetic cream EMLA covered with an adhesive transparent plastic dressing for 30 minutes, before injection.

Inclusion Criteria:

• Every subject who did not meet any of the exclusion criteria, and signed the informed consent, was included in the study

Exclusion Criteria:

• Subjects younger than 18
• Subjects that suffered from any local or systemic sensitivity alteration
• Subjects that suffered from any cognitive deficit
• Individuals allergic to any of the components of the anesthetic ointment EMLA (eutectic mixture of lidocaine 2,5% and prilocaine 2,5%).

Outcomes were studied by an investigator that did not participate in the practical part of the trial.