The hookworm inoculation rash
A successful inoculation with hookworms frequently causes an itchy, pink and possibly raised rash at the inoculation site as a result of the immune system reacting to the worms’ entry into the skin. This rash may appear within a few hours, or may take 2 or 3 days to appear. Occasionally, the entry sites may take on a bruised appearance, with black and blue discolouration.
Some people may have a rash without itching.
Others can experience itching but no rash, and some may have no physical signs whatsoever.
If there is no rash
An absence of any indication that the larvae have entered the skin is especially likely if the self-treater is taking an immunosuppressant drug such as prednisone/prednisolone. Even low-dose steroids, such as those used in inhalers, can profoundly reduce the skin reaction to inoculation, although a few subjects who are taking steroids may still develop an itch and/or rash.
In a few cases, a lack of any skin response may indicate that the larvae failed to survive the rigours of the journey, perhaps as a result of them being exposed to extremes of temperature during transit, especially at altitude during flight, where everything at or near the edge of a pallet will freeze. For more information about this possibility, see Storage and survival of hookworm larvae.
The absence of a rash may not indicate a failed inoculation
If there is still no visible confirmation in the first 3 days that inoculation was successful, it might be assumed that the larvae were all dead, but they may not be.
In the absence of a rash, the subject may be tempted to add more worms immediately. However, it is advisable to wait rather than immediately order a replacement dose because side effects can appear suddenly, “out of nowhere”, a few weeks after an apparently unsuccessful inoculation, confirming that the original dose was viable after all.
If these individuals had added a second dose of larvae within the first 12 weeks, they would have faced the possibility of having to run the gauntlet of greatly increased side effects which could have been so severe as to necessitate termination. It may therefore be wise, in the absence of a skin response, to wait for several weeks before reinoculating. One individual who did this after getting no rash, only very minor itching, and no other obvious symptoms in the first few days, suddenly developed the typical gastrointestinal side effects three weeks later, including bloating, nausea, diarrhoea and significant fatigue.
The absence of a rash may not predict reduced side effects
Determining whether inoculation was successful
In the absence of an obvious skin response, there are two approaches that can help to determine whether or not inoculation was successful.
1. If you had a full blood count (CBC) and/or IgE levels taken just before inoculation, you could retest a couple of weeks after the inoculation. If there has been an increase in eosinophils, this would suggest that infection is likely, although there are other factors that can influence eosinophil levels.
2. The only definitive test is stool analysis, which can be carried out once the worms begin producting eggs between 4 and 6 weeks post inoculation. For more details, see Stool testing (egg counting).
Number of red dots may not correspond with number of larvae inoculated
When there is a rash at the inoculation site, the number of red dots that appear does not necessarily indicate the number of larvae that have entered the skin. Since larvae tend to clump together and are microscopic, several may enter in close proximity, leaving what looks to the naked eye like a single entry point.
Also, the entry of a single larva can cause what appear to be multiple entry sites.
With no reliable one-to-one, worm-to-spot relationship, the number of visible entry points can only provide a rough guide to the number inoculated.
Timing, severity and duration of itching
If there is itching, this often commences within a few minutes of applying the bandage/dressing, but it can be delayed for a number of hours, and its duration can vary enormously, from a few minutes to several weeks. The severity of itching and whether it is continuous or intermittent also vary considerably, with occasional itching at the inoculation site being possible at any time during the first few weeks and even occasionally as late as 4 months or more.
Skin response may not necessarily predict outcome
Persistence of the rash
The rash may persist for at least 7 weeks in some cases.
And the rash can reappear intermittently over an even longer period.
In one case involving a 4-year-old boy with a suspected mast cell disorder, a third inoculation of 10 NA caused a persistent rash and also reactivated the rash at the site of his second inoculation (also 10 NA). Both rashes then remained “constantly itchy/painful and bumpy” for 7 months until a helminthic therapy-aware doctor recommended high doses of antihistamines and mast cell medications, which quickly resolved the rash. The problem in this case was likely to have been that the number of larvae inoculated was too high for a child with a suspected mast cell disorder. (See Helminthic therapy and mast cell disorders for more about the use of HT in subjects with MCAD/MCAS.)
Future reactivation of the rash
The inoculation site may suddenly flare and become itchy again weeks or months after an inoculation. This might occur when the worms start to attach to the inner wall of the intestine to feed for the first time on or after day 21, or at the peak of the immune response to a new batch of worms at around 7 weeks.
This phenomenon may be the result of the L3 larvae having shed their cuticles and sheaths during their migration through the host’s skin.  When the immune system detects similar material during the later stages of the worms’ migration, and when they begin to feed from the intestinal wall, there is a release of antibodies to those types of cells or proteins wherever they occur, including in the skin, which can flare as a result.
Inoculation sites may also flare temporarily following new immune challenges. For example, one self-treater experienced a rash at an old inoculation site when exposed to the sun for the first time in a while.  And others have had old rash sites flare after contracting COVID-19.  
Treating the itch
After self-inoculation with hookworm larvae, the bandage/dressing should be left in place for a minimum of four hours and, ideally, for twelve. If the larvae are applied in the morning, the bandage/dressing can be removed before going to bed at night, making it easier to treat the itch and thus prevent sleep being lost as a result of discomfort during the night. Although some people prefer to inoculate just before going to bed because they can sleep through the itching.
If the resulting rash is itchy, this can be treated after removal of the bandage/dressing.
An electric hair dryer - gold star tip!
An electric hair dryer provides the gold standard treatment for a hookworm itch. Hot air is directed from the dryer at the centre of the rash and held up to the point of feeling momentary pain. This will usually stop the itch completely for a number of hours, but one does need to be careful not to cause a burn! More details here.
The The Bite Away device
Like hair dryers, some devices marketed for the treatment of insect bites and stings use heat to nuke an itch, and these can be effective for the rashes caused by inoculation with a small number of NA larvae.
Since these devices are pocket-sized and battery-powered, they are also very portable. However, they do cause intense, if momentary, pain with each application, and they need to be applied accurately to each entry point, which can become tedious when dealing with a larger inoculation rash with many entry points. These devices may also not be fully effective if a few larvae have travelled laterally beneath the surface of the skin while hunting for a suitable blood vessel. In such cases, a hair dryer is the better option.
One hookworm host has reported that taking this blend of plant sterols and sterolins got rid of her inoculation itch for hours. 
Oral antihistamine products
Oral antihistamines may help to relieve the itch but, unfortunately, some of these contain drugs that have anthelmintic properties. While it is unlikely that anything will harm hookworms before they attach to the gut mucosa (towards the end of the third week, post inoculation) some of these drugs may harm mature hookworms. The following guide is intended to help navigate the available antihistamine drugs.
Topical products containing 2% diphenhydramine hydrochloride are very effective and are available in several forms. An alcohol-based version may perform marginally better than a cream, but whichever form is used, diphenhydramine is ideal because it works as an antihistamine as well as a local anaesthetic. Available in both the US and UK - from Amazon, Ebay and other outlets and may also be available in other countries.
- Benadryl Extra Strength Itch Stopping Cream
- Benadryl Extra Strength Itch Stopping Gel
- Benadryl Extra Strength Spray
- Benadryl Extra Strength Itch Relief Stick
A maximum strength (1%) hydrocortisone cream is another treatment option for the itch, e.g.
- In the US: Equate Maximum Strength 1% Hydrocortisone Anti-Itch Cream, 2 oz
- In the UK: Galpharm Bites & Stings Relief Cream, 10 grams.
The more potent, prescription-only topical corticosteroid, mometasone, may be more effective than hydrocortisone.
Non-steroidal creams and lotions
Any topical allergy or itch treatment - such as vaginal itch relief creams - should work to varying degrees, and other treatments that have been reported to work include the following.
- Calamine lotion One individual says this gives him at least two hours relief, and someone else, who had tried Benadryl lotion, prednisolone, cortisone cream, “some sort of anti/itch numbing spray” and oral antihistamines, has claimed that calamine lotion beats them all. 
- Aveeno lotion. Another hookworm user who has tried "all kinds of anti-itch medicines/ treatments" says that Aveeno Daily Moisturising Lotion helps her the most. 
- Egoderm Cream 1% (Ichthammol/ Tumenol Ammonium/ ammonium bituminosulfonate). 
- Florasone Cream (containing Cardiospermum tincture) brought relief to one user.
- Zinc oxide cream. Typically used to treat nappy / diaper rash, this effectively dries out the blisters if applied once or twice each day. You can get higher concentrations on Amazon if the standard supermarket ones don't cut it. 
Anything that moisturises the skin can help to ease the itch, especially once any oozing has stopped and the rash site is dry.
Several essential oils have been reported to help, including sandalwood oil  and magnolia oil. While the latter worked in the short term to control the itch and prevent scratching,  ice can also be effective, and it's cheaper! 
Lavender, rosemary and ylang ylang essential oils contain beta-carophyllene, which helps speed wound healing and also reduces the chances of scar tissue.  Two drops of lavender oil, applied on a bandage, calmed one user’s itch almost immediately and allowed her to forget about the rash completely. 
The quality and purity of essential oils may influence the extent of their beneficial effects.
Magnesium sulphate (Epsom salts)
One hookworm host has had success using an Epsom salts (magnesium sulphate) solution. This reportedly eased the itch, stopped the weeping and generally dried up the rash site. 
Others have used magnesium sulphate paste with similar success.
Someone else who applied Epsom salts as a paste also found that it worked, but said it was messy. 
This product combines aluminum sulfate tetradecahydrate with calcium acetate monohydrate. Together with water, these astringent ingredients form aluminum acetate.
Domeboro Medicated Soak worked wonders for one self-treater's rash.
Domeboro is also available as a cooling gel, which might be more convenient for treating a hookworm rash.
Others have reported success with a variety of substances, including honey, natural pawpaw cream, sea or salt water and even toothpaste!
Toothache gel has also proved to be successful.
One self-treater was particularly impressed with the results of using snail mucin. 
Someone else found relief from applying alcohol.
Adding a small dose of TSO
Several NA hosts have found that taking a dose of between 83 and 250 TSO two hours before inoculating with NA reduces their skin response to the hookworms, perhaps by distracting the immune system from the activity at the inoculation site.
Even taking the TSO after inoculation with NA has helped in one case.
Other NA hosts have found that, while regularly taking 250 TSO every 2 weeks, their NA inoculation rashes have resolved much more quickly. They commented, in particular, on a marked shortening of the oozing stage.
And one self-treater has had success with even an extremely small dose of TSO.
For how to divide the contents of a bottle of TSO, see Dividing doses.
Keeping the rash covered
One person says that she finds the best way to deal with the itch is not to touch the rash at all with fingers, creams or clothes, etc., as any friction over the area increases the itch. So, while it’s hard to achieve, she finds that just keeping the rash covered and restraining her urge to touch it is what works best for her. Another agrees about covering the rash.
Some people have found it helpful to apply pressure to the rash using an elastic bandage.
Striking the rash
A few others have reported getting up to half a day’s relief from the itch after giving their rash several hearty slaps. In one case this is done after applying hydrocortisone cream.
An ice pack has been found to provide effective relief by some people.
Managing an angry, weeping rash
This section applies to the rashes produced by supplementary inoculations rather than a first inoculation.
A pumice stone or other abrasive
Once there are pronounced yellow heads or blisters at the points of entry, scrubbing away everything that stands above the skin surface can bring remarkably swift relief from the itching and help reduce the possibility of swelling. This is probably because the scrubbing removes the debris left behind by the larvae when they entered the skin, thus taking away what the immune system was reacting to.
A rough towel, loofah, or surgical nail brush may remove the heads, but a pumice stone can be even more effective.  One hookworm host uses a men's pocket hair comb to scrape/rake repeatedly across the area, with the long edge of the comb aligned in parallel to the direction of movement. Another uses her fingernails  and one brave helminthophile pours table salt onto the rash and scours this with a paper towel,  although someone else who tried this commented that it "Burns like the dickens for a while!" 
Removing the heads will leave shallow craters which may weep, sometimes quite profusely, for a few days. However, the fluid released is just exudate, or serous drainage. It is very unlikely to be suppuration (pus).
There have been no reports to date of infections taking hold at inoculation sites, even when the skin is broken, and this may be because the heightened immune activity around the rash defeats any opportunistic bacteria. There should therefore be no need for the use of antibacterial preparations.
Keeping the site covered with a thick, absorbent dressing will help prevent staining of one's clothes. Panty liners are excellent for this purpose.
Clay poultice / lavender oil
One self-treater has found that following up the scrubbing with a clay poultice and/or lavender essential oil provides even more benefit.
Dickinson's Witch Hazel
Dickinson's Witch Hazel, dabbed on with cotton balls has provided soothing relief for the rash and a 75% reduction in swelling, itching and weeping within approximately half an hour. 
Some people have applied the homeopathic remedy, graphites, to their oozing rash, and this can be purchased as a cream, e.g., Nelsons Graphites Cream 30g. However, there have been no reports as to how effective this might be in the case of a hookworm rash.
Someone else applies a bandage covered in normal table salt, claiming that this "makes all the liquid come out really fast, and helps dry the scabs real soon." 
Combining treatment options
After trying out several different treatment approaches over many inoculations, self-treaters will often settle on a range of options that they combine to make their inoculation routine far less eventful than it would otherwise be.
For example, one NA user who, without remedial measures, always experiences a severe reaction to every inoculation, starts by taking the maximum permitted dose of a hookworm-safe antihistamine just before inoculating, along with a small dose of TSO obtained by drawing off 1.5 ml of liquid from a bottle of 2,500 TSO. The antihistamine helps reduce the initial itch, and the TSO helps to distract the host’s immune system away from the new NA.
This self-treater inoculates early in the day so that the bandage can remain in place for 12 hours before he goes to bed. When the bandage is removed, he applies hot air from a hairdryer to the inoculation site (see above for details), and repeats this as required during that first night and throughout the second day.
Yellow peaks will have started to appear at the entry points by the second evening, and these are scoured off using a pumice stone before he goes to bed. Provided that the site is re-scoured whenever there is any sign of itching, the worst of the itch is effectively over from 36 hours after the inoculation, and healing of the entry points will have begun, with only minimal oozing from that point onwards.
The use of this particular combination of treatments by this individual has greatly reduced the severity of the itch, the degree of oozing from the entry points, and the extent of the area of "angry”, red, swollen cellulitis that previously always appeared around, and for several inches beyond, the inoculation site. And it has shortened the entire healing process by a couple of days.
Development of inoculation rashes over time
The first few hookworm doses tend to produce a successively more pronounced skin rash as a result of memory cells keeping a record of their previous encounter with the organism. 
The fourth and fifth inoculations can leave some people with a very angry-looking bright red rash which can develop fluid-filled blisters/vesicles that may ooze exudate or serous drainage.
Occasionally, someone may experience the worse rash after their sixth inoculation.
Some people begin to experience less severe rashes after the fourth or fifth inoculation.
Others can continue to get very angry and itchy rashes indefinitely.
Some people may eventually develop an additional area of inflammation extending for several inches around the rash and perhaps even affecting most of the upper or lower limb used for the inoculation. This area of cellulitis may appear bruised, can be quite swollen, and may also be as itchy as the rash itself. Once this reaction has presented, it seems to reoccur with each subsequent inoculation.
But some successful supplementary inoculations may fail to produce any reaction.
Others have reported their experience of the intensity of the inoculation rash after each dose of NA in this Support group thread.
In a few people, the rash severity may reduce significantly after hookworms have been hosted for more than 6 years.
The possibility of marking/scarring at the inoculation site
Hookworm inoculation does not leave a permanent scar, but can cause temporary scarring and leave a visible mark that persists for a time. This marking may appear to be permanent if the same site is used repeatedly.
Some areas of skin appear to be less likely to develop marking/scarring.
The risk of temporary scarring can be reduced by spreading the larvae around the bandage/dressing, thus preventing any areas of particularly intense inflammation.
If the same site is always used for inoculation, this area may, over time, develop a semi-permanent, faintly mottled "shadow" of slightly darkened skin, which is another reason to use a less visible area for inoculation. (See Body sites used for hookworm inoculation.)