Bụi gây dị ứng.

• bụi = dust
• gây = to cause
• dị ứng = allergy, allergic reaction, or to be allergic depending on context

So the structure is basically:

• bụi → subject
• gây → verb
• dị ứng → result/effect

A very direct breakdown is Dust causes allergy/allergic reactions.

It is actually quite similar to English here.

The pattern is:

• Bụi = subject
• gây = verb
• dị ứng = object/result

So Vietnamese is following a normal Subject + Verb + Object/Complement order:

• Bụi gây dị ứng.
• Dust causes allergies.

This sentence is straightforward and does not use any special inversion or unusual grammar.

Vietnamese usually does not require articles like English does.

So bụi can mean:

• dust in general
• dust as a substance
• dust particles

In a general statement like Bụi gây dị ứng, Vietnamese simply uses the noun by itself.

English often needs an article or some other determiner, but Vietnamese often does not:

• Mèo ngủ. = Cats sleep / The cat is sleeping, depending on context
• Bụi gây dị ứng. = Dust causes allergies

Context tells you whether the meaning is general or specific.

This is a very common learner question because Vietnamese words are flexible.

dị ứng can behave like:

• a noun: allergy
• a verb/adjectival expression: to be allergic

In Bụi gây dị ứng, it is best understood as the thing being caused:

• cause allergies
• cause an allergic reaction

So here, thinking of dị ứng as a noun-like result is the most helpful.

Compare:

• Tôi bị dị ứng. = I have an allergy / I’m having an allergic reaction.
• Tôi dị ứng với bụi. = I’m allergic to dust.
• Bụi gây dị ứng. = Dust causes allergies.

Vietnamese often does not mark tense explicitly when the time is clear from context.

So Bụi gây dị ứng naturally reads as a general present-time fact:

• Dust causes allergies
• Dust can cause allergies

If you wanted to make time clearer, Vietnamese could add time words:

• Hôm nay bụi gây dị ứng nặng hơn. = Today dust causes worse allergic reactions.
• Trước đây tôi không bị dị ứng với bụi. = I wasn’t allergic to dust before.

But for general truths, no tense marker is needed.

Neither in the English sense.

bụi is usually treated like a mass noun, similar to English dust. It does not normally need a singular/plural ending.

So:

• bụi = dust
• not really a dust or dusts in normal usage

Vietnamese nouns generally do not change form for singular or plural. Quantity is shown only if needed:

• nhiều bụi = a lot of dust
• ít bụi = little dust

The main thing to notice is the tones.

• bụi → has a heavy falling tone on ụ
• gây → mid/rising-type contour depending on accent; no strong marked tone sign beyond the circumflex on â
• dị → heavy tone
• ứng → rising tone

A rough learner-friendly guide:

• bụi ≈ boo-ee with a short, heavy stop-like ending feeling
• gây ≈ somewhat like gay, but with Vietnamese vowel quality
• dị ứng ≈ zee/yi uhng is not accurate, but it reminds you there are two syllables and both tones matter

More importantly, pronounce it as four syllables:

• Bụi / gây / dị / ứng

Do not blend dị ứng into one English-like word.

Yes, it is natural, especially in general statements, health advice, or warning-style language.

It sounds like:

• Dust causes allergies
• Dust triggers allergic reactions

Depending on context, native speakers might also say:

• Bụi có thể gây dị ứng. = Dust can cause allergies.
• Bụi dễ gây dị ứng. = Dust easily causes allergies / is likely to cause allergies.
• Tôi dị ứng với bụi. = I’m allergic to dust.

So your sentence is natural, but other versions may sound more specific or more conversational.

They describe the situation from two different angles.

• Bụi gây dị ứng = Dust causes allergies.
  This focuses on dust as the cause.

• Tôi dị ứng với bụi = I am allergic to dust.
  This focuses on the person experiencing the allergy.

A useful contrast:

• gây = cause
• dị ứng với = be allergic to

So if you want to say what produces the problem, use gây.
If you want to say what someone reacts badly to, use dị ứng với.

Usually gây is the better choice.

• gây is the standard verb for cause
• làm often means do, make, or make something become...

For medical, formal, or neutral statements, gây dị ứng is much more natural than làm dị ứng.

So:

• Bụi gây dị ứng. = natural
• Bụi làm tôi bị dị ứng. = possible in some contexts, but less neat and less standard for this general statement

If you are talking about symptoms, health effects, or side effects, gây is very common.

No.

Classifiers are used in Vietnamese mainly when counting or specifying individual items. But bụi here is a mass noun, so no classifier is needed.

Examples:

• Bụi gây dị ứng. = Dust causes allergies.
• Có nhiều bụi trong phòng. = There is a lot of dust in the room.

You would only need extra words if you wanted to count containers, piles, particles, and so on:

• một lớp bụi = a layer of dust
• một đám bụi = a cloud of dust

But in your sentence, just bụi is correct.