Good, glad to hear she hasn't those signs.
Though if she has responded to the antihistamine that may be because it is sedating her but it may also reflect a possible airway irritation as opposed to being sick.
So, do monitor her but I would suggest putting her on a liquid antacid (ie Milk of Magnesia - 0.5tsp ever 12-24 hours). That way we counter nausea but also coat her throat if it is irritated. As well, we can plan to put her on a soft/light diet like cooked white rice with boiled chicken, boiled white fish, cottage cheese, scrambled eggs, or meat baby food (as long as its garlic/onion free). There are also OTC vet diets that can be used (ie Hill’s I/D or Royal Canin’s sensitivity) too. The aim of these diets is that they will be better tolerated/absorbed by the compromised gut. Therefore, it should get more nutrients in and result in less GI upset. As long as improvement is being seen, I usually advise continuing this until the signs are settled, and then weaning her slowly back to her normal diet.
Overall, her signs do raise a few concerns but if she is responding the the antihistamine this may be an upper airway/throat irritation. Therefore, we can try broad supportive care for Luna. Of course if this persists, then we'd want a check with her vet to have her stomach and airway assessed +/- have antibiotics started if they find an infectious process is to blame.
Afterwards, as I am giving you my own free time, please take a moment & rate me with the **STARS** (or leave a written rating of 1-5; 5 being great). Otherwise the site won't credit me for helping you. There is no extra charge for this & rating me now does not close your question. We can continue until you are satisfied, simply use the reply box and let me know. Thank you! : ) **