What can I do if I have symptoms of oregano oil overdose?

If severe - go to ER. Rash?, Vomiting? Tingling? The worst symptom would be internal swelling that prevents you from breathing and it would leave you no time if that happened. So, precautions are wise. If symptoms are mild and improving, just watch and have a plan unless you feel frightened. This is a riskier product than it sounds. Be careful. Best!
Stop taking it. first and foremost, stop taking the oregano oil. if the symptoms are GI related (diarrhea), replace the good bacteria lost with a probiotic. if symptoms are more severe, related to liver (yellow skin, eyes, dark urine etc) or do not improve see your medical provider. hope this helps.