Is contact allergy to preservatives, antioxidants and fragrances an additional factor influencing the treatment rosacea?

Introduction
Topical treatment and daily skin care are the biggest challenges in the treatment of rosacea. The treatment is long lasting and particularly difficult because of poor tolerance to skin care products.

Objective
A search for factors that can influence the progress of rosacea among contact allergens, and to find out why are some patients resistant to the therapy. A detailed analysis involved fragrances, anti-oxidants and preservatives.

Material and methods
Patients with complicated rosacea were tested for contact allergies. The testing was performed between 2010 and 2017 in a group of 269 patients. The patients were divided into two groups: tested before and tested after 2014. The reason for this division was a different distribution of positive tests for certain allergens before and after 2014.

Results
62.8% of patients had erythematotelangiectatic rosacea (ETR), 15.6% had papulo-pustular rosacea (PPR), 21.6% had both ETR and PPR. Among fragrances, the fragrance mix and balsam of Peru most frequently gave the positive result. After 2014, among phenolic antioxidants a positive reaction to dodecyl gallate increased from 5.6% to 20.0% in the first reading, and from 12.7% to 46.4% in the second reading. High proportion of positive results were seen for octyl gallate and paraben mix. For preservatives, positive reactions were recorded for 0.02% water solution of methylisothiazolinone (MIT) and methylchloroisothiazolinone (MCI), benzyl alcohol and phenoxyethanol. After 2014, reaction caused by propolis was observed.

Conclusions
In treatment-resistant cases of rosacea, standard procedures should include testing for contact allergens. The first and the second reading are equally important for the further therapy.