Skin ulcer is a common disease with complicated etiopathogenes, which makes it hard to be cured. It has been reported that photodynamic therapy (PDT) can be used to treat skin ulcers which were caused by different diseases. However, PDT is an expensive treatment and patients always experience obvious pain during or after the treatment, which hinders the application of PDT in skin ulcer. Our previous study found that PDT using a low concentration of 5-Aminolevulinic acid (ALA) could promote the healing of skin ulcer without obvious adverse reactions, which suggests us that low concentration ALA-PDT might be an efficient and cost effective treatment in skin ulcer. To further investigate the use of low concentration ALA-PDT in skin ulcer, we plan to recruit patients with skin ulcers caused by different diseases, and divide these patients into different groups according to their causes of disease, and then treat them using low concentration ALA-PDT to observe the healing process of skin ulcer. This study could further optimize and promote the use of low concentration ALA-PDT in skin ulcer.

Inclusion Criteria:

• chronic skin wounds that involved the dermis and did not heal in three months or did not exhibit a tendency toward healing

Exclusion Criteria:

• allergies to photosensitizers and their solvents, serious medical illnesses, such as severe heart disease, severe liver or kidney dysfunction, systemic infection or any concomitant infection that would require treatment with an additional antimicrobial agent, the use of topical or systemic antibiotics within one month prior to treatment. Pregnant or lactating women were also excluded.