029-22 – Can affective touch reduce histamine induced itch severity?

Itch, defined as an unpleasant sensation evoking the desire to scratch, is a commonly experienced dermatological issue experienced by 8.4% of the general population. Approximately 22% of individuals experience itch lasting for more than three weeks (chronic itch). Itch, or pruritus, has many causes, one of those being the release of histamine from dermal mast cells which activate histamine-sensitive peripheral afferents. The primary afferents that signal itch belong to the group of peripheral unmyelinated C-fibres. Research has shown that C-fibres signal both itch and pain with significant overlaps between the modalities where pain has been shown to reduce itch. However, C-fibres can also signal for pleasant touch by the means of C-tactile afferents (CTs). CTs belong to C-fibres and respond to slow caressing touch at velocities of 1-10cm/s. Given how pain and itch overlap at the peripheral level and itch can be modulated by pain, this would indicate that itch can also be modulated by pleasant touch. Therefore, we are aiming to investigate whether affective touch can reduce histamine induced itch intensity. It is hypothesised that affective touch will reduce itch to a greater extent than non-affective touch. We aim to recruit 60 healthy subjects where we will induce itch on volar forearm of subjects via histamine iontophoresis. Subjects will then receive a total of 3 blocks of affective touch (3cm/s), non-affective touch (18cm/s) and tapping on the skin presented in a counterbalanced order for 18 trials. Subjects will then rate the pleasantness of touch as well as itch intensity using a VAS. The Touch Experiences and Attitudes Questionnaire (TEAQ) and Pain and Vigilance Questionnaire (PAVQ) will be used to assess individual differences. Data will be analysed using a linear mixed effects model (IV: stroking type, DV: VAS scores). Time-point will be used as a covariate and individual differences measures will be correlated with perceived pleasantness of touch.