green spots

Have you taken a look at their moodlets? One of the moodlets have to be dazed moodlet called Poisoned. Here's some information about poisoning:
Poisoning can start by many ways:
1. Jungle spider, bee and plasma bat attacks.
2. Some chance cards when exploring the jungle.
3. Temple defences: Arrow trap.
4. Trying to pass through a gate guarded with poisonous gas.
5. Rare Marked for Death curse. (Either by Zatatoil death relic or after opening treasure chests)

Recognizing poisoning and results:
Poisoned sims have green spots on their skin and will burp green mist. Sims also get dazed moodlet.
The first stage Feeling Icky lasts for 12 hours. When the moodlet expires, sim may either recover from poisoning or get worse. The notification will pop up telling how your sim's contition went.
The second stage Poisoned lasts for 3 days. If sim got poisoned by Marked for Death curse, they'll immediately start by this stage. From then on, your sim may not recover from it by themselves and require antidote.
The third stage Overwhelmingly Poisoned lasts for 8 hours. After that, sim will die and their ghost has a green cloud around them.

Obtaining antidote:
Once sim get poisoned, they can obtain antidote by two ways:
1. Asking for it from locals. This requires bonedust, which is either obtained from temple traps or excavations.
2. Buying it from computer (Find one in museum if you don't want to end the vacation). It costs 1,000 simoleons there.
After getting one, just have your sim drink it and poisoning will be gone.

Avoiding next poisoning cases:
Here's three ways to avoid poisoning cases:
1. Either get equipment to fend off spiders, bees and bats or get your sim's fitness and logic skills high.
2. Read and choose the options carefully. If chance card requires high level in skill your sim doesn't have, don't do it.
3. Examine traps before triggering them. Find the right switch.
If all else fails, it's always good to have some antidote backup with you.

If you max out your Selvedoradan Culture skill (Which you can do in one evening by chatting to the locals about things to do with Selvadorada) you can buy bone dust from the market vendors. Then you can ask one of your new friends for the antidote.

"5782341b77vl;c-16418273" wrote:
Donate 250 Simoleons to the town statue will rid all of your Sim's curses.

It only works if sim got poisoned by curse. If sim gets poisoned by spiders, temple traps etc, this won't work.
Poisined state by itself isn't a curse. It's a challenge that sim can either overcome or die by it. You don't have option to donate if your sim doesn't have any curses.

It sounds like your sim has been poisoned and needs to get an antidote, or else she will eventually die. You can order the antidote by computer (there is a computer in the museum), or, if you have bone dust in your inventory, you can use that to negotiate with a local to provide you with an antidote (I haven't done this myself, so I'm not too sure how it works). The easiest is to order the antidote by computer.

Donate 250 Simoleons to the town statue will rid all of your Sim's curses.