Summer's Eve ??

everytime I use Summer's <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> my vagina gets really itchy both on the outside. if I don't use it it doesn't itch and I know I don't have any stds. and I never have a reaction the day I use it but the day after I do. how come this happens?