Is there any side effects of eating prawns?

Depends on details: That's like asking, "Is there any side effects of eating chocolate," or "... eating chicken," or "eating SPAM," etc... It all depends on the details, such as: food allergies and intolerances, pregnancy status, how much is eaten, how often it's eaten, how it's cooked, what's added to it before eating, where it is grown or caught, how it's processed, etc... Details matter. Otherwise, food is food.

Prawns: Some people are allergic to prawns and there is some concern for others that the crustacean could be contaminated with pollutants. However, prawns have been shown to have a number health benefits and anti-inflammatory properties.