yakhyo deokbune jaechaegiga jogeum deol na.

약효 means the effect of a medicine or the medicine’s effectiveness.

• 약 = medicine
• 효(효과) = effect

So 약효 덕분에 means something like thanks to the medicine working or because of the medicine’s effect.

덕분에 is used when the result is seen as positive or helpful, like thanks to in English.

So:

• 약효 덕분에 = thanks to the medicine’s effect
• 약효 때문에 = because of the medicine’s effect

Both can be translated similarly, but 덕분에 sounds more positive and appreciative. Since sneezing less is a good result, 덕분에 fits naturally.

That is normal because 덕분에 attaches directly to a noun.

So the pattern is:

• Noun + 덕분에

Examples:

• 친구 덕분에 = thanks to my friend
• 약효 덕분에 = thanks to the medicine’s effect

You do not add 이/가 or 은/는 before 덕분에 here.

Because the verb here is 나다, and with 나다, the thing that happens is usually marked with 이/가.

So:

• 재채기가 나다 = sneezing happens / a sneeze comes out

In Korean, this is a very common way to talk about bodily reactions or symptoms. The sneeze is treated as the subject of the verb, not the object.

Compare:

• 재채기를 하다 = to do a sneeze / to sneeze
• 재채기가 나다 = a sneeze comes out / to sneeze

Both are possible, but 재채기가 나다 is very natural for involuntary physical reactions.

Yes — and that is exactly the idea here.

In 재채기가 나, the verb is 나다, which often means:

• to come out
• to arise
• to occur

So 재채기가 나다 literally feels like a sneeze comes out or sneezing occurs.

This use is very common with physical conditions and reactions:

• 기침이 나다 = to cough / a cough comes out
• 땀이 나다 = to sweat / sweat comes out
• 열이 나다 = to have a fever / fever comes up

So 나 here does not mean I go out or anything like that. It is the casual present form of 나다.

It could, but the nuance is a little different.

• 재채기해 = I sneeze / I am sneezing
• 재채기가 나 = sneezing comes out / I sneeze

Both are understandable, but 재채기가 나다 sounds especially natural for an involuntary bodily symptom or reaction. Since sneezing is not usually something you choose to do, 나다 works very well.

So this sentence sounds natural because it frames sneezing as a symptom that has lessened due to the medicine.

덜 means less.

It is used when something happens to a lesser degree than before or less than expected.

So:

• 덜 나 = happens less / comes out less
• 조금 덜 나 = happens a little less

In this sentence, 덜 modifies 나다, so the meaning is that sneezing is occurring less than before.

조금 means a little.

So 조금 덜 나 means:

• happens a little less
• I sneeze a bit less

It softens the statement. The speaker is not saying the sneezing is completely gone — only that it has reduced somewhat.

No. It suggests that the sneezing is less than before, not completely gone.

Because of 덜 and 조금, the meaning is more like:

• I’m sneezing a little less now
• The sneezing has eased a bit

If the speaker wanted to say it stopped, they would use a different expression, such as something meaning it stopped or it doesn’t happen anymore.

나 is the casual/plain intimate form, often used in conversation with friends, family, or when speaking informally.

Forms of the same sentence:

• 약효 덕분에 재채기가 조금 덜 나. = casual
• 약효 덕분에 재채기가 조금 덜 나요. = polite
• 약효 덕분에 재채기가 조금 덜 납니다. = formal

So the ending tells you about the speech level, not a major change in core meaning.

Korean often leaves out the subject when it is obvious from context.

So even though I is not stated, the sentence naturally means something like:

• I sneeze a little less thanks to the medicine
• My sneezing is a little better thanks to the medicine

In everyday Korean, omitting subjects is very common when the listener can figure them out from context.

Yes, it implies a comparison with a previous or usual state.

The sentence suggests:

• before the medicine, the speaker sneezed more
• now, because of the medicine, the sneezing has decreased somewhat

Even though the earlier state is not stated directly, 덜 automatically implies less than before or less than some standard.