Histamine in tears in allergic rhinoconjunctivitis

Abstract

The classic clinical symptoms of allergic conjunctivitis (type I allergy)--itching and lacrimation--are the effect of histamine. Determination of histamine levels in tears may be useful in evaluating the dynamics of local histamine release in connection with the clinical findings. Between 1.7.1994 and 31.6.1995 we analyzed the histamine levels in tears and investigated the clinical symptoms (score of 0-3) of 32 hyposensitized pollen-sensitive patients (14 males and 18 females, aged 18-45 years, group I) and of 32 controls (group II) without any allergic disease, performed in each case once in season and once out of season. Tear production and composition were measured by Schirmer's test and tear break-up time at the same time. The histamine levels of the tear samples (obtained by microcapillary method) were analyzed by electrochemical determination. In group I there was a highly significant increase of the mean histamine level from 0.89 +/- 2.22 ng/ml (out of season) to 7.71 +/- 7.51 ng/ml (in season) for the right eye and from 0.73 +/- 2.36 ng/ml (out of season) to 9.51 +/- 9.07 ng/ml (in season) for the left eye (P = 0.0000). The histamine level in tears of the controls (group II) was below the detection limit in all samples. The seasonal histamine level were higher with the severity of atopy (Erlangen atopy score). There was no significant influence of age and gender. The reduction of allergic symptoms during hyposensitization was not comparable to the degree of seasonal histamine level. Compared with the clinical findings, the histamine level in tears did not correlate with the symptoms of lacrimation, itching and conjunctival hyperemia. The histamine level in tears alone is not useful as a marker for the clinical severity of this atopyassociated disorder and for the efficacy of the anti-allergic therapy. After standardization of the determination method and the identification of other soluble mediators simultaneously, the histamine level in tears can be used as one part of a profile of mediators to evaluate the clinical symptoms.