Dear No germs,
Your wife’s symptoms, coupled with the fact that she has refused to see a psychiatrist, tells me that her problem, if any, is not diagnosed and is probably currently untreated.
The coping strategy of giving in to her demands for increasingly higher standards of hygiene is not tenable as she may either be unaware that her anxieties are growing or that she is unable to manage them. Individuals with conditions like these rarely manage it on their own without some professional assistance. This can take the form of seeing a psychiatrist and working with a psychotherapist trained to treat such conditions. Whilst a complete cure may elude some, most are able to manage their anxieties and thereby their condition.
Now comes the hard part. Because your wife may be in denial or is more focused on trying to reduce her immediate anxieties, you, and perhaps with the help of others, may have to present it to her. In a firm but gentle way, clearly outline the behaviours that are unreasonable and do not get distracted by the reasons behind them. Many of these anxieties often persist because there is a tiny grain of truth that supports it. For example, with the pandemic, the possibility of catching a new viral strain is always there but it should not debilitate us. Share with your spouse that help is available to address some of her fears. If she is still reluctant to see a psychiatrist, you both can begin by seeing a psychotherapist who can help her examine her misgivings and concerns.