assuage, relieve, ease, still, quench, slake, alay, appease, placify, pacify, more...

exacerbate, worsen, intensify

quell, calm, relieve, soothe, ease, mitigate, temper, more...

french, great, gross, lewd, common, little, same, ancient, small, equal, bitter

quell concerns,   reduce fear,   diminish fears,   calm fears,   mitigate concern,   ease worries,   assuage ones doubts,   make less scary,   lighten the doubt,   worry no more