Saint John's wort (Hypericum perforatum) was recognised as a traditional, folk medicine used topically for the treatment of wounds, abrasions, burns, sunburns and inflammatory skin disorders.

Its use in wound healing could be justified with its anti-inflammatory, antimicrobial and astringent effects. It also stimulated tissue growth and cell differentiation, as one of Hypericum perforatum's main ingredients, hyperforin, was shown to activate TRPC6 channel which had been recognised as an activator of keratinocyte differentiation. Another potentially useful activities could be its inhibitory effects on epidermal Langerhans cells.

Furthermore, in vivo research showed its potential with improved wound healing in different rat models. Finally, several clinical studies were performed testing its effects in atopic dermatitis treatment, wound healing after caesarean section and episiotomy, as well as healing of post-surgical scalp wounds, bed sores and venous ulcers.

The aim of the study will be to determine the effectiveness of ointment containing Hypericum perforatum oil on promoting skin recovery in different human skin damage models on healthy volunteers, in comparison to placebo.

Chosen test sites will be the forearms. One forearm will be treated will the formulation containing Hypericum perforatum oil while the other will be treated with the placebo formulation. Four test sites will be marked on each forearm with skin barrier damage induced on three areas while the fourth will be left intact. Treated forearm and test sites sequence on forearms will be prospectively randomized (double randomization).

First skin damage model used in the trial will be sodium lauryl sulphate (SLS) induced irritation. The SLS solution will be placed on the skin of participants under the occlusion for 24 hours. Second model will be the tape-stripping procedure with defined TEWL value set as an endpoint. The final model will be damage by the UV radiation. UV irradiation will be performed under strict conditions with use of the necessary safety equipment. Only the defined test areas will be irradiated with the defined dose of radiation.

Inclusion Criteria:

- young, healthy volunteers who gave written informed consent

Exclusion Criteria:

• skin disease, skin damage on measurement sites
• use of corticosteroids, antihistamines and immunomodulators a month prior the inclusion and during the trial
• use of drugs that may cause photosensitivity
• use of emollients three days prior the inclusion in the trial
• non-adherence to the trial protocol
• exposure to artificial and excessive natural UV radiation
• pregnancy and lactation
• skin cancer
• history of vitiligo, melasma and other pigmentation and photosensitivity disorders
• immunosuppression
• allergic or irritant reactions to the constituents of the two ointments (active and placebo) and similar chemicals (e.g. salicylic and benzoic acid)