The phrase 'harmful side effect' is correct and usable in written English.
You can use it to describe a negative outcome that was not necessarily predicted or intended. For example, "The drug was meant to reduce pain, but it came with a very dangerous and potentially harmful side effect that caused extreme nausea and vomiting."
And just as the free-agent market has turned minions into millionaires, it has had a harmful side effect: the scheming sports agent.
He explains: "Understand that, dammit, science marches on and that, someday very soon, someone's going to invent a P.E.D. that works very well without even the hint of harmful side effect with which everyone can justify their moral outrage when they lose their, well, stuff in the public prints.
Traditional formulations of the proportionality condition require that the value of promoting the good end outweigh the disvalue of the harmful side effect.
Among these phenomena, the Urban Heat Island (UHI) is known as the most harmful side effect of the urbanization which affects the Outdoor Air Quality OAQQ).
One harmful side effect of Sarbox is that it disproportionately hurts small businesses by burdening them with relatively huge accounting compliance costs and is therefore a barrier to smallish companies going public.
The most plausible and defensible version of the principle of double effect requires that the harmful side effect be minimized, so the principle of double effect provides no justification for withholding hydration and nutrition in cases in which death is not immediately imminent.
Some drugs interact with one another, altering their effectiveness and even resulting in harmful side effects.
Therefore, there is a need to develop novel therapeutics that can effectively treat infectious dermatological diseases without harmful side effects.
Changes in the dose could be effective in order to diminish the harmful side effects.
And many responses have harmful side effects.
Harmful side effects might turn up unexpectedly.
