I have long been skeptical of boosting the immune system. Like 'support', it is a red flag that the product is probably bunkum.

As an ID doctor, to my mind boosting, if it could be done, would be to cause an pro-inflammatory response and a pro-inflammatory response is pro-thrombotic. Every infection evaluated is associated with an increased risk of stroke, heart attack or pulmonary embolism.  So if the immune system really could be boosted, it would probably result in an increase risk of a vascular event.  Fortunately, as best I can tell, all over the counter immune system boosters don't.

There is a product called Immutides Spray that is supposed to boost the immune system.

It is an oral spray consisting of proline-rich polypeptides derived from pigs milk. According to the web site

Unlike most immune supplements which randomly boost the immune response, PRPs stimulate or calm the immune system as needed. Since the spray is applied directly into the mouth, it delivers the right response at the right time.

Their "Science" page is blank, but proline-rich polypeptides do have a wide variety of immunomodulatory effects:

PRP possesses immunoregulatory properties, including effects on humoral and cellular immune responses, shows regulatory activity in Th1 and Th2 cytokine induction, and has the ability to inhibit the overproduction of reactive oxygen species and nitric oxide. PRP has also shown psychotropic properties.

So I am impressed they have a formulation that can stimulate or calm immunity as needed.

What proline-rich polypeptides have not been used for is treatment of human TB or HIV. But that did not stop it from being tried, unsuccessfully,  in South Africa:

The Eastern Cape Health Department has instructed hospitals to give an untested medicine to patients with tuberculosis. It has not received ethical approval to proceed with this clinical trial. Now it appears the project has been scrapped, apparently after the Treatment Action Campaign (TAC) asked the national government to intervene.

GroundUp has obtained a memo that the manager of the Nelson Mandela Bay Health district, Dr LP Mayekiso, sent to three hospitals on 27 January. The memo instructs the hospitals to start dispensing Immutides Spray to patients with tuberculosis (TB) from 1 March. “The goal is to boost the immune system of patients so badly affected by TB that they need admission to hospital,” says the memo. It also says, “All these patients must stay on Immutides for the remainder of their TB treatment.”

As Noseweek suggested

The rollout appears to have been a cynical, predatory scheme that would have raked in millions for a politically well-connected “natural health” products company.

Given the seriousness of HIV and TB, one would wonder why anyone would use a product that  has not been "evaluated by the Food and Drug Administration" and "is not intended to diagnose, treat, cure or prevent disease".  I guess TB and HIV are not diseases.  The company denies any wrong doing.

Unethical experimentation upon AIDS patients using unproven supplements seems to be an ongoing problem in Africa:

This is not the first time the government has involved itself in unlawful trials. In the mid-2000s a vitamin salesman, Matthias Rath, ran an unauthorized clinical trial on AIDS patients. Rath was close to the National Minister of Health at the time, the late Manto Tshabalala-Msimang. She had refused to stop Rath’s activities.

And Big Pharma is portrayed as unethical.

Perhaps what is needed is an Epicaizo spray?