Cross‐reactivity between methylisothiazolinone, octylisothiazolinone and benzisothiazolinone using a modified local lymph node assay

Abstract

In the light of the exceptionally high rates of contact allergy to the preservative methylisothiazolinone (MI), information about cross‐reactivity between MI, octylisothiazolinone (OIT) and benzisothiazolinone (BIT) is needed. To study cross‐reactivity between MI and OIT, and between MI and BIT. Immune responses to MI, OIT and BIT were studied in vehicle and MI‐sensitized female CBA mice by a modified local lymph node assay. The inflammatory response was measured by ear thickness, cell proliferation of CD4+ and CD8+ T cells, and CD19+ B cells in the auricular draining lymph nodes. MI induced significant, strong, concentration‐dependent immune responses in the draining lymph nodes following a sensitization phase of three consecutive days. Groups of MI‐sensitized mice were challenged on day 23 with 0·4% MI, 0·7% OIT and 1·9% BIT – concentrations corresponding to their individual EC3 values. No statistically significant difference in proliferation of CD4+ and CD8+ T cells was observed between mice challenged with MI compared with mice challenged with BIT and OIT. The data indicate cross‐reactivity between MI, OIT and BIT, when the potency of the chemical was taken into account in choice of challenge concentration. This means that MI‐sensitized individuals may react to OIT and BIT if exposed to sufficient concentrations.