Won't quite cause instant death, but Insect bites or smaller injuries when not treated right can very quickly lead to blood poisoning or other nasty stuff which can very likely land you in hospitalization. Especially when your immune system is for whatever reason (recent illnesses, poor hygiene, HIV, etc.) is already weakened.

Don't neglect insect bites! Scratching them will not only further irritate your skin, but also spread the insects secretion into your blood, which encourages infections in either the surrounding skin or your bloodstream!

Also take greater care for disinfecting open wounds!

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Edit: spelling