Kamagra may sometimes cause severe side effects, such as abnormal heartbeat, chest pain, ankle swelling, dizziness, a painful and unusually lasting (4 hours) erection, arrhythmia and an allergic reaction. These adverse effects justify stopping treatment and looking for medical care. However, the majority of side effects are mild and transient, including flushing, nausea, headache, stomach upset and nasal congestion. On the other hand, if these moderate Kamagra adverse effects became persistent, it would time to inform your local doctor.