It appears that about 1 person in 300 people has an allergic-type reaction to vitamin D within days.
   (Have no specific reference - it is just an impression from reading 12,000+ articles on vitamin D)
The allergic reaction may include itchy skin, hives, and intestinal upset.
The reaction is real, and the cause varies
Possible reasons and solutions
- The reaction is typically due to a lack of Magnesium - Mg is required by Vitamin D
 Solution take Magnesium supplement for a week and try again
- It might be similar to reaction to the sun - probably previously known
 Red-heads and others - try a smaller dose initially
 See also Photosensitivity (sun allergy) and vitamin D
- Does size too big - at least initially
 Perhaps we need to start with a smaller dose, say 1000 IU, and get used to vitamin D for a week or so
- Might be a reaction to Vitamin D2 Vets determined that D2 should not be given to any mammals
 Solution - use Vitamin D3, not D2
- The reaction by the gut
 Try a sublingual form
 Try a gut friendly or topical form
 Try a vitamin D patch on the skin
 Try a processed form (calcitriol, etc.) - click on the chart below for details
 Try an injection (lasts longer) - click on the chart below for details
- Reaction to the fillers (oil, etc.), additives, coloring, the gelatin capsule
 Try a pure and clean form such as by Bio-Tech Pharmacal
- Rare reaction to Wool/Lanolin 
 Try a plant form of D3
- Extremely rare reaction to Vitamin D3 in regular/processed forms
 Use sun or UV bulb to generate Vitamin D in your skin - click on the chart below for details
- Interaction of vitamin D with a prescription drug is very rare to have a drug reaction
- Rare mutation of CYP24A1 gene results in Vitamin D accumulating
Many ways to increase Vitamin D
See also VitaminDWiki
- People allergic to Lanolin should not be allergic to vegan Vitamin D
- Woman with rare allergy to vitamin D was desensitized in a single day – Dec 2016
- Side Effects and Warning for vitamin D
 Excessive thirst, Metal taste in the mouth, Poor appetite, Weight loss, Bone pain, Tiredness, Sore eyes, Itchy skin, Vomiting, Diarrhea, Constipation, A frequent need to urinate, Muscle problems
- All items in category Interactions141 items (virtually all interactions = Drug reduces the vitamin D effectivity, no reaction 
- Vitamin D interactions with drugs – Oct 2011 Abstract says which drugs, but no amount of interaction
- Headache with vitamin D may mean you need Magnesium
- Response and adverse effects of 20,000 and 30,000 IU Vitamin D weekly - Feb 2015
- On-line survey of drug uses and side effects – including vitamin D
 Which contains the following table:Note This is a % of the small % who had any reaction to vitamin D 
 Perspective: 3X more likely to be allergic to Aspirin than to Vitamin D- How Do I Know if I Am Allergic To Aspirin? 1%
- Aspirin - Not just for pain relief anymore 1%
- An Aspirin Allergy and its Relationship to a Salicylate Allergy 1%?
 
 Repeat the above information - for cut and paste as of Jan 2016 About 1 person in 300 gets a reaction to vitamin D 
 That rare reaction is due to the following 9 reasons
 Lack of Magnesium
 Reaction to the sun (if already known)
 Does size too big initially
 Reaction to Vitamin D2, not D3
 The reaction by the gut
 Reaction to additives, fillers, colors, etc.
 Rare reaction to Wool
 Extremely rare reaction to Vitamin D in any form
 Extremely rare Interaction with a prescription drugshort URL = http://is.gd/allergictod 
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