عندي حساسية من البنسلين

You use this phrase exactly like you would in English. Place the condition after عندي. It works in every Arabic dialect from Morocco to Iraq. You don't need fancy grammar here. Just state it clearly and wait for the nod of understanding. If you are at a pharmacy, say it before they hand you a box. If you are at a hospital, say it during your intake.

Use this anytime a medical professional is involved. Use it when a friend offers you a random pill for a headache. Use it when filling out medical forms at a new gym or clinic. It is also helpful to mention if you are traveling with a group. Let your tour guide know just in case of emergencies. Better safe than itchy (or worse)!

Don't use this at a restaurant unless they serve medicine for dessert. For food allergies, you swap البنسلين for the food item. Don't use it metaphorically to mean you 'dislike' someone. In English, we might say 'I'm allergic to bad vibes.' In Arabic, this sounds literal and confusing. Stick to the medical context to avoid strange looks.

Modern medicine in the Arab world is highly advanced. However, people still look out for one another deeply. If you mention an allergy, expect a lot of follow-up questions. People might ask, 'Since when?' or 'Is it severe?' This isn't prying; it's communal care. The term حساسية is well-understood by everyone from grandmothers to surgeons.

You can change the substance easily. Swap البنسلين for الفول السوداني (peanuts) or السمك (fish). If you want to ask someone else, say هل عندك حساسية؟ (Do you have an allergy?). In some dialects, people might just say عندي فوبيا (I have a phobia) for non-medical fears. But for penicillin, stick to the script. Your health is the priority here.