Thank you Tereza,
Now as I am sure you can appreciate for my questions, there are a few potential causes for the sign you are seeing. Since you are seeing no changes to the skin itself, we can at least put worries about fungal infections and bacterial infections lower on our list of concerns for Lucky. With that, we need to focus on this likely being an allergic response to the fleas, to foreign material that are coming in regular contact with his chin (food bowls be the most common trigger), or dietary allergies.
First, to soothe the itch and at the same time rule out allergic skin disease (flea saliva induced or any of our allergies), you can consider treating him with an anti-histamine. Anti-histamines can settle allergic skin to all of the above (provided the trigger allergen isn’t in continued contact) in mild cases. Typically in these cases, we will use Piriton for these wee ones (ie 1-2mg or 1/4 – 1/2 tablet of a 4mg Piriton tablet up to twice daily). Do note that while anti-histamines will break that itchiness cycle and give his skin the chance it needs to settle, it can make kitties drowsy. Therefore, we always keep the dose low and if he were to be drowsy on this, then we'd reduce the dose to once daily for him. And of course, this medication shouldn't be used if your kitty has any pre-existing conditions or are on any other medication without speaking to your vet. That all said, if you treat him with this and he doesn't settle or his irritation is very severe, then he may require a short course of steroids to allay the allergic skin response and associated itchiness.
Next, as I noted above, we can see focal skin reactions linked to feeding/water dishes. Even if he has had this dish for years, it is possible to still develop an allergy, react to bacterial loads on the dish, or even to the cleaner use to wash the dish. Therefore, it would be ideal to try him with an alternative bowl at this point. Ideally, we would want to use one made of non-porous material (so bacteria cannot hide and fester). And you do want to make sure that you are using a dish that you clean thoroughly on a regular basis. Furthermore, since we most often see facial skin reactions/allergies with plastic bowls, do make sure not to use one with him for the next wee while. Instead, consider trying a stainless steel or ceramic dish for him. (Do note that it can take 4-6 weeks for the allergic reaction to fully subside of the bowl was the trigger).
Further to addressing potential allergens, we do want to address the chin itself (to continue to keep infection away). Therefore, we'd want to be cleansing the area on a regular basis (potentially after eating) with a mild antiseptic. Examples of mild antiseptics that are safe to use in the area are salt water (1tbsp salt to a pint warm water) or dilute chlorohexidine (available at most pharmacies OTC). Bathing of this region should be performed 2-3 times daily, then the area should be dried thoroughly. If he is still trying to scratch it in the short term as you treat with the antihistamines, you can also consider placing a buster collar to protect the area.
Furthermore, if your kitty has general issues with his skin being sensitive, you may also want to consider trying essential fatty acid (EFA) supplementation. EFA’s are the fats that are part of skin cells composition and play a role in their health and coat growth. They are often used therapeutically in the management of a number of feline skin disorders. So, if he has underlying compromised skin cell health this can aid in settling his skin. A general recommendation for dietary supplementation with essential fatty acids is based on supplying 1.5-2.5 ml fish oil for a 4kg cat. Alternatively, you can offer a small volume of fresh salmon weekly. If he isn't keen on fish, then there are alternatives that your vet can provide. Examples of oral EFA supplements include Viacutin (LINK) or Yumega (LINK). As well, there is a spot on preparation that gets around a kitty even having to ingest these EFAs, called Allerderm (LINK).
Overall, with a lack of visible skin changes supporting infection, we have to appreciate that allergy based causes are most likely triggering his itchy chin. Therefore, do consider trying him with an anti-histamine while cleansing the area and protecting it from his dirty claws. Furthermore, since we do have to be concerned about contact allergens, do consider a swap in bowls for the short term and potentially going back to feeding diets you know have not tolerated itchiness for him before.
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
All the best,
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