Me sorprende que no te hayas puesto peor, siendo tan alérgica a los mosquitos.

Both are possible, but they are built differently and feel slightly different.

• Me sorprende que... = It surprises me that...
  • This is very common in Spanish.
  • The thing that causes surprise is the grammatical subject: que no te hayas puesto peor...
• Estoy sorprendido/a de que... = I am surprised that...
  • Also correct, but it sounds a bit more like describing your state.

In your sentence, me sorprende que... is a very natural way to express reaction to a situation.

Because me sorprende que... expresses an emotion or reaction, and in Spanish that normally triggers the subjunctive in the following clause.

So:

• Me sorprende que + subjunctive

That is why you get:

• no te hayas puesto peor

and not:

• no te has puesto peor

This is one of the very common uses of the subjunctive: after verbs and expressions of emotion, evaluation, surprise, etc.

Examples:

• Me alegra que vengas.
• Me molesta que hables así.
• Me sorprende que no te hayas puesto peor.

Hayas puesto is the present perfect subjunctive.

It is used here because the sentence refers to something connected to the present: the person has not gotten worse up to now, and that current result is what surprises the speaker.

So the structure is:

• haya/hayas/haya... + past participle
• here: hayas puesto

Compare:

• Me sorprende que no te hayas puesto peor.
  = I’m surprised you haven’t gotten worse.
• Me sorprendió que no te pusieras peor.
  = I was surprised that you didn’t get worse.

So hayas puesto fits the idea of a recent or still relevant situation.

Here, ponerse means to become or to get.

So:

• ponerse peor = to get worse / to become worse

This is a very common Spanish pattern:

• ponerse enfermo/a = to become ill
• ponerse nervioso/a = to get nervous
• ponerse triste = to become sad
• ponerse peor = to get worse

In this sentence, it refers to the person’s physical reaction becoming more severe.

Because ponerse is a pronominal/reflexive verb here, and the pronoun changes depending on the person:

• me pongo
• te pones
• se pone
• nos ponemos
• os ponéis
• se ponen

Since the sentence is talking to you singular, it uses te:

• que no te hayas puesto peor

So this literally works like that you have not gotten yourself worse, although in natural English we just say that you haven’t gotten worse.

Because poner is irregular.

Its past participle is:

• puesto

not ponido

So:

• he puesto
• has puesto
• ha puesto
• hayas puesto

Other common irregular past participles:

• hacer → hecho
• ver → visto
• decir → dicho
• romper → roto
• volver → vuelto

This phrase gives background or a reason-like idea.

• siendo = being
• tan alérgica a los mosquitos = so allergic to mosquitoes

So the phrase means roughly:

• considering that you’re so allergic to mosquitoes
• since you’re so allergic to mosquitoes
• being so allergic to mosquitoes

It explains why the speaker is surprised.

This use of the gerund in Spanish often adds context, cause, or circumstance, not just an ongoing action.

Spanish often uses the gerund to make the sentence more compact and fluid.

So these are similar in meaning:

• Me sorprende que no te hayas puesto peor, siendo tan alérgica a los mosquitos.
• Me sorprende que no te hayas puesto peor, ya que eres tan alérgica a los mosquitos.
• Me sorprende que no te hayas puesto peor, como eres tan alérgica a los mosquitos.

The version with siendo sounds natural and concise. It is common in written and spoken Spanish when giving background information.

Because the adjective agrees with the person being spoken to.

• alérgica = feminine
• alérgico = masculine

So if the speaker is talking to a woman, they say:

• siendo tan alérgica

If speaking to a man:

• siendo tan alérgico

This agreement is a basic but important feature of Spanish adjectives.

Because in Spanish, the adjective alérgico/a takes the preposition a.

So:

• ser alérgico/a a algo

Examples:

• Soy alérgico al polen.
• Es alérgica a los gatos.
• Eres alérgica a los mosquitos.

English learners often want to use de, but with alérgico/a, Spanish uses a.

Because Spanish often uses the definite article when talking about things in a general sense, especially after certain adjectives and prepositions.

So:

• alérgica a los mosquitos = allergic to mosquitoes

This does not mean only some specific mosquitoes. It can still mean mosquitoes in general.

This is very common in Spanish:

• Me gustan los perros. = I like dogs.
• Es alérgica a los gatos. = She’s allergic to cats.
• Tengo miedo a los perros. = I’m afraid of dogs.

Peor means worse.

In this sentence, it works as the complement after ponerse:

• ponerse peor = to get worse

It does not need an article or anything extra here.

Compare:

• Está peor. = He/She is worse.
• Se puso peor. = He/She got worse.
• No te hayas puesto peor. = You haven’t gotten worse.

Normally, no.

Spanish uses peor as the standard comparative form of malo/mal:

• malo / mal → peor

So you say:

• Está peor
• Se puso peor

not usually:

• está más mal
• se puso más mal

You may occasionally hear más mal in some contexts or regions, but for standard Spanish, peor is what you should use here.

Tan means so.

It intensifies the adjective:

• alérgica = allergic
• tan alérgica = so allergic

Here it helps show why the speaker finds the situation surprising. The idea is:

• given how allergic you are to mosquitoes, I’m surprised you didn’t get worse

So tan adds emphasis.

The subject is the whole clause beginning with que:

• que no te hayas puesto peor, siendo tan alérgica a los mosquitos

That entire idea is what surprises the speaker.

So structurally, it is like:

• [That you haven’t gotten worse...] surprises me

This is why the verb is sorprende and not something agreeing with me. The me is an indirect object: it surprises me.

Because Spanish usually omits subject pronouns when the verb already makes the subject clear.

In:

• no te hayas puesto peor

the form hayas already shows the subject is tú.

So Spanish naturally leaves out tú unless it wants emphasis, contrast, or clarity.

You could say:

• Me sorprende que tú no te hayas puesto peor...

but that would sound more emphatic, as if contrasting with someone else.

Yes. A learner might hear or use simpler alternatives, for example:

• Me sorprende que no estés peor, siendo tan alérgica a los mosquitos.
• Me sorprende que no te encuentres peor, siendo tan alérgica a los mosquitos.

These are slightly different in nuance:

• no te hayas puesto peor focuses on not having gotten worse
• no estés peor focuses on not being worse
• no te encuentres peor focuses on not feeling worse

The original sentence is very natural and idiomatic, but there are other ways to express a similar idea.

Yes, it sounds perfectly natural in Spain.

Nothing in it is especially regional in a way that would confuse learners. The grammar and vocabulary are standard:

• me sorprende que...
• ponerse peor
• ser alérgico/a a...
• siendo...

So this is a good example of natural everyday Spanish, including a very useful subjunctive pattern.