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Prepositions after adjectives

Harmless: from or to?

Harmless normally takes to when describing something that does not cause damage. Harmless from is not a standard adjective-preposition combination in current English.

Quick answer

Use harmless to

Use harmless to to say that something does not hurt or damage someone or something. Harmless from is generally not idiomatic. If you want to mention protection, use safe from or free from instead.

The insect is harmless to humans.
This medicine is harmless to most pets.
The joke seemed harmless to everyone present.

Choose the pattern by meaning

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

1
harmless to + person/animal

Saying something does not cause harm

Use harmless to for people, animals, or living things not affected negatively.

These spiders are harmless to humans.
The plant is harmless to cats.
2
harmless to + object/process

Saying something is safe for something

Harmless to can also describe things that are not damaged or affected.

The cleaner is harmless to painted surfaces.
This update is harmless to your files.

See the difference in context

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

Construction
Example
Meaning
harmless to
The substance is harmless to children.
standard pattern meaning not dangerous
harmless from
The phrase is generally not idiomatic.
not a standard complement after harmless
safe from
The building is safe from flooding.
protected against danger
free from
The product is free from artificial colours.
without something unwanted

Common mistakes

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

Using harmless from

English normally uses harmless to, not harmless from.

✕ The chemical is harmless from humans. ✓ The chemical is harmless to humans.

Confusing harmless with safe from

Harmless describes the thing causing no damage; safe from describes protection against danger.

✕ The town is harmless from storms. ✓ The town is safe from storms.

Using harmless with negative meaning

Harmless means not dangerous or not damaging.

✕ The dog is harmless to visitors because it bites. ✓ The dog is not harmless to visitors because it bites.

Omitting the preposition

Harmless usually needs to before the affected person or thing.

✕ This spray is harmless plants. ✓ This spray is harmless to plants.

Quick practice

Choose the expression that matches the intended meaning.

1. These insects are harmless ___ people.
2. The cabin is safe ___ wild animals.
3. This product is harmless ___ painted walls.

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Frequently asked questions

Is harmless from ever correct?

It is not a standard modern English pattern. Use harmless to instead.

What is the difference between harmless to and safe from?

Harmless to describes something that does not cause harm. Safe from describes protection against danger.

Can harmless describe jokes or comments?

Yes. A harmless joke or comment is not intended to hurt or offend.

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