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Eosinophils are a major cause of tissue injury in allergic conjunctivitis. The biological nature of eosinophils in the conjunctiva and the mechanisms that control eosinophils' responses in allergic conjunctivitis are currently not completely understood. This study reports that conjunctival eosinophils comprise two populationsdSiglec-F int and Siglec-F hi din different life stages. Siglec-F int eosinophils partly expressed CD34 and were in the immature (or steady) state. Siglec-F hi eosinophils did not express CD34, sharply increased in number after short ragweed (SRW) pollen challenge, and were in the mature (or activated) state. Moreover, chemical sympathectomy by 6-hydroxydopamine reduced the recruitment and activation of eosinophils, whereas the activation of the sympathetic nerve system (SNS) with restraint stress accelerated the recruitment and activation of eosinophils in SRW-induced conjunctivitis. It was also found that two eosinophil populations expressed alpha-1a-adrenergic receptors (a1a-ARs); in SRW-induced conjunctivitis, treatment with an a1a-AR antagonist decreased eosinophil responses, whereas treatment with an a1a-AR agonist aggravated eosinophil responses. Thus, eosinophil responses in conjunctivitis are regulated by the SNS via a1a-AR signaling. SNS inputs or a1a-AR function may be potential targets for the treatment of allergic conjunctivitis.