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Prepositions after adjectives

Unhealthy for, to, in, about, or by?

Unhealthy is most commonly followed by for when talking about harmful effects. Other prepositions usually belong to a different part of the sentence rather than directly following the adjective.

Quick answer

Which preposition goes with unhealthy?

Use unhealthy for to describe something harmful to a person, body part, relationship, or situation. Unhealthy to is also used before a person or animal. Phrases with in, about, or by usually add extra information rather than complete the adjective itself.

Too much sugar is unhealthy for children.
That level of stress is unhealthy for a team.
The smoke is unhealthy to breathe.
They live in an unhealthy environment.

Choose the pattern by meaning

These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.

1
unhealthy for + person or thing

Showing harmful effects

Use unhealthy for when something negatively affects someone or something.

Fast food is unhealthy for your heart.
Constant conflict is unhealthy for a marriage.
2
unhealthy to + verb

Describing harmful actions

Use unhealthy to before some infinitives, especially with actions affecting health.

It is unhealthy to skip meals regularly.
It can be unhealthy to work every night.
3
unhealthy in + area

Describing conditions within something

In usually introduces a place, situation, or area where unhealthy conditions exist.

The air quality is poor in unhealthy workplaces.
Researchers found high stress in unhealthy environments.
4
unhealthy about + behaviour

Talking about attitudes or habits

About can follow unhealthy when referring to attitudes, obsessions, or behaviour patterns.

She has something unhealthy about her obsession with fame.
There is nothing unhealthy about asking for help.

See the difference in context

The same subject can take different constructions because each sentence answers a different question.

Construction
Example
Meaning
unhealthy for
Smoking is unhealthy for your lungs.
harmful to someone or something
unhealthy to
It is unhealthy to ignore severe stress.
harmful or unwise action
unhealthy in
Children grew up in unhealthy conditions.
in introduces a place or situation, not the adjective pattern
unhealthy about
There is something unhealthy about his fixation on money.
describes an aspect or attitude
unhealthy by
The patients were weakened by unhealthy living conditions.
by usually introduces a cause or agent, not a standard complement of unhealthy

Common mistakes

Some combinations appear in real text but do not mean what learners often assume.

Using by as the main complement

By normally introduces a cause, not the adjective pattern after unhealthy.

✕ The food is unhealthy by children. ✓ The food is unhealthy for children.

Confusing for and to

Use for with people or things affected. Use to mainly before verbs.

✕ Skipping sleep is unhealthy for stay alert. ✓ Skipping sleep is unhealthy to stay alert.

Using about for physical harm

About usually refers to attitudes or behaviour, not direct health effects.

✕ Salt is unhealthy about your heart. ✓ Salt is unhealthy for your heart.

Treating in as the adjective complement

In often introduces a location or situation rather than completing unhealthy.

✓ They worked in an unhealthy environment.

Quick practice

Choose the expression that matches the intended meaning.

1. Too much caffeine is unhealthy ___ teenagers.
2. It can be unhealthy ___ work without rest.
3. They lived ___ unhealthy conditions for years.

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Frequently asked questions

Is unhealthy for the most common pattern?

Yes. Unhealthy for is the standard pattern for harmful effects on people or things.

Can I say unhealthy to?

Yes. It is mainly used before verbs, such as unhealthy to smoke heavily.

Is unhealthy by correct?

Not usually as a direct complement. By more often introduces a cause, such as harmed by unhealthy habits.

ubiquitous in, on, across, throughout or for? "ugly in", "ugly for" or "ugly of"? ultimate in, of, for, on or as? "unacceptable to", "unacceptable in" or "unacceptable for"? unaccounted for unaccustomed to or in? unacquainted with unaffected by, in, for or with? "unaffordable for" or "unaffordable to"? unanimous in, on, about, regarding or for? "unattractive to" or "unattractive for"? "unavailable for" or "unavailable to"?

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