kahun no sei de, kyou ha me ga kayui desu.

のせいで means because of or due to, but it usually implies that the cause is something bad, annoying, or unwanted.

So:

• 花粉のせいで = because of the pollen
• natural nuance: because of pollen (and that’s causing a problem)

That makes it a very good fit with itchy eyes.

A useful comparison:

• 雨のせいで、試合が中止になった。
  Because of the rain, the game was canceled.
• あなたのおかげで、助かりました。
  Thanks to you, I was saved/helped.

So せいで is often negative, while おかげで is often positive.

Both can talk about cause, but they feel a little different.

• 花粉で目がかゆいです。
  My eyes are itchy because of pollen.
• 花粉のせいで目がかゆいです。
  My eyes are itchy because of pollen, and pollen is to blame.

のせいで sounds a bit stronger and more complaint-like. It highlights that the speaker sees pollen as the reason for the unpleasant situation.

So the original sentence has a natural feeling of Ugh, pollen is making this happen.

Here, 今日は makes today the topic or time frame:

• 今日は = as for today / today

It does not necessarily mean strong contrast, but it can give a sense of speaking specifically about today.

So:

• 今日は目がかゆいです。
  My eyes are itchy today.

Without は, 今日 could still work in many cases, but 今日は is very common and sounds natural when setting the scene.

You can think of it as:

• As for today, my eyes are itchy because of pollen.

In this sentence, 目がかゆい is the most natural pattern.

With body parts and feelings/sensations, Japanese often uses:

• [body part] が + adjective

Examples:

• 頭が痛い = my head hurts / I have a headache
• 喉が痛い = my throat hurts
• 目がかゆい = my eyes are itchy

Here, が marks the thing experiencing the condition: the eyes are itchy.

If you said 目はかゆい, it would sound more contrastive, like:

• As for my eyes, they’re itchy
  perhaps implying something else is not.

So 目がかゆい is the neutral, standard choice here.

Japanese often leaves out information that is obvious from context.

In a sentence about a physical sensation like itchy eyes, the listener naturally understands that the speaker means my eyes, unless there is some special reason to say otherwise.

So:

• 目がかゆいです naturally means my eyes are itchy

Not:

• the eyes in general are itchy

Similarly, 私は is omitted because the speaker is obviously talking about their own condition.

This kind of omission is extremely common in Japanese.

Japanese often uses the singular form of body parts even when English would use the plural.

So:

• 目がかゆい often means my eyes are itchy
• 耳が痛い can mean my ears hurt
• 手が冷たい can mean my hands are cold

Context tells you whether one or both are meant. Since pollen commonly affects both eyes, English usually translates it as eyes.

If you really wanted to specify plural, you could say 目がかゆい anyway in normal speech. Japanese usually does not need to mark the plural here.

かゆい is an い-adjective, and in modern Japanese it is perfectly normal to add です after it to make the sentence polite.

So:

• casual: 目がかゆい。
• polite: 目がかゆいです。

This is a very common pattern:

• 暑いです = It’s hot
• 高いです = It’s expensive
• かゆいです = It’s itchy / My eyes are itchy

What you do not say is:

• かゆいだ ✘

That is incorrect, because だ does not follow an い-adjective.

かゆいです is natural and grammatical.

That said, depending on tone, a native speaker might also say:

• 目がかゆい。
  casual
• 目がかゆいです。
  polite
• 目がかゆいんです。
  polite, with a slightly explanatory or complaint-like tone
• 花粉のせいで、今日は目がかゆくて…。
  sounds like the speaker is leading into more explanation

So the original form is fine. It is a standard polite sentence.

In のせいで, the で is part of the expression.

• X のせいで Y = Y happens because of X
• X のせいだ = It is X’s fault / It is because of X

Examples:

• 渋滞のせいで遅れた。
  I was late because of traffic.
• 風邪のせいで学校を休んだ。
  I missed school because of a cold.

So in your sentence, 花粉のせいで connects the cause to the result:

• cause: pollen
• result: my eyes are itchy today

The sentence breaks down like this:

• 花粉のせいで = because of pollen
• 今日は = as for today / today
• 目が = my eyes / eyes
• かゆいです = are itchy (polite)

So the full structure is:

• [Cause] + [time/topic] + [body part] + [condition]

A very literal translation would be:

• Because of pollen, as for today, my eyes are itchy.

More natural English:

• Because of pollen, my eyes are itchy today.
• My eyes are itchy today because of pollen.

Yes. Japanese word order is flexible as long as the particles stay correct.

For example, these are all possible:

• 花粉のせいで、今日は目がかゆいです。
• 今日は、花粉のせいで目がかゆいです。
• 目が、花粉のせいで今日はかゆいです。
  grammatical, but less natural in most contexts

The original sentence is natural because it starts with the cause, then sets the time, then gives the main statement.

So it flows like:

• Because of pollen, today, my eyes are itchy.

It strongly suggests that, yes.

• 花粉 = pollen
• 目がかゆい = eyes are itchy

Together, this commonly suggests pollen allergy / hay fever symptoms.

A native speaker would likely understand this as:

• My eyes are itchy because of pollen in the air
• probably seasonal allergies

If you wanted to be even more explicit, you might say:

• 花粉症で、今日は目がかゆいです。
  Because of hay fever, my eyes are itchy today.

But the original sentence is already very natural and easy to understand.