here are several common side effects that can occur after neuromodulator treatment. Some are related to injections; some are related to the ingredient that makes neuromodulators effective wrinkle-reducers. The most common side effects include redness, swelling, and bruising. A headache isn’t always going to happen. If it does, it’s believed that it occurs because the treated muscle tightens or spasms before it gradually relaxes into a mild, temporary state of paralysis. The muscle spasm feels like a general headache. You might resolve this side effect with an over-the-counter pain reliever. Should you develop a headache after receiving Botox or another neuromodulator like Xeomin, Dysport, or Jeuveau, this side effect should go away naturally after two or three days.