Clinical and histological profiles of guinea pig conjunctiva undergoing late-phase reaction (LPR) were evaluated before and after additional antigenic challenge. Four groups of animals were passively sensitized with IgGl antibodies, challenged with the specific hapten di-DNP-lysine, and rechallenged during LPR either with di-DNP-lysine, or with PBS, or with an aspecific antigen to characterize the reactivity of the inflamed conjunctival tissues. The course of the clinical anaphylactic responses was modified slightly only by challenge with a specific hapten during LPR. However, no significant changes in the inflammatory cell profile were observed in conjunctiva undergoing LPR after an additional challenge. This suggests the participation of mechanisms which may mediate the attenuation of the anaphylactic response in physiologic conditions of persistent antigen provocation.